Review Article - Journal of Experimental Stroke & Translational Medicine (2012) Volume 5, Issue 1

Strategies for therapeutic hypometabothermia

*Corresponding Author:
Shimin Liu, M.D., Ph.D
Department of Neurology, Boston University School of Medicine
715 Albany street, C329, Boston, MA02118
Tel: 617-638-7776
Fax: 617-638-5354


Although therapeutic hypothermia and metabolic suppression have shown robust neuroprotection in experimental brain ischemia, systemic complications have limited their use in treating acute stroke patients. The core temperature and basic metabolic rate are tightly regulated and maintained in a very stable level in mammals. Simply lowering body temperature or metabolic rate is actually a brutal therapy that may cause more systemic as well as regional problems other than providing protection. These problems are commonly seen in hypothermia and barbiturate coma. The main innovative concept of this review is to propose thermogenically optimal and synergistic reduction of core temperature and metabolic rate in therapeutic hypometabothermia using novel and clinically practical approaches. When metabolism and body temperature are reduced in a systematically synergistic manner, the outcome will be maximal protection and safe recovery, which happen in natural process, such as in hibernation, daily torpor and estivation.


Hypothermia; metabolic suppression; cold adaption; thermoregulation; neuroprotection


Hypometabothermia: hypometabolism and hypothermia


Neuroprotective means for ischemic stroke is desperately needed in clinical settings because thrombolytic treatment can only be delivered to a very limited fraction of stroke patients. Therapeutic metabolic suppression and hypothermia are troubled with severe complications. While investigators are desperately in searching for an effective and safe neuroprotective means for critical illness, nature has already provided a solution for these problems millions years ago.In hibernators body temperature can reach -1.97 ºC, metabolic rate can be reduced to 1.22% of euthermic base levels,(Buck and Barnes 2000; Karpovich et al 2009)1, 2(Buck and Barnes 2000; Karpovich et al. 2009)(Buck and Barnes 2000; Karpovich et al. 2009)and cerebral blood flow can drop below ischemic threshold, (Frerichs et al 1994) which are followed by complete recovery. The efficacy and safety in therapeutic hypometabothermia can be greatly improved by utilizing the strategies that hibernators use for surviving extreme living conditions. This is supported by: 1) hibernation is associated with differential expression of conserved genes, rather than novel hibernation specific genes,(Zhao et al 2010) human shares similar genome with hibernating mammals;(Andrews 2007) 2) human have the capability for enduring extremely low temperature; successful recovery from accidental hypothermia with body temperature reaching 16 °C has been reported, (Wollenek et al 2002) 3) human can also enter into some kind of “pseudo-hibernation” status; loska, "winter sleep", was reported to be a common practice among ancient Russian peasants in the Pskov Government, where Russian peasants were alleged to spend half year in sleep for dealing with famine; (BMJ1900 2000) practicing meditation can lower metabolic rate and enter a “pseudo-hibernation” status; Indian yogis being studied under laboratory conditions demonstrated their ability to drastically reduce metabolic rate and survive air-tight confinement for up to 8 days without injury. (Young and Taylor 1998)Although it is not possible to directly put human into hibernation, but what we have learnt from hibernation can make a difference in treating ischemic strokes.

Current problems and barriers in therapeutic hypometabothermia

Therapeutic hypothermia provides robust protection but it is troubled by thermoregulatory defenses

Hypothermia therapy for patients is almost always counteracted by thermoregulatory defenses,(Sessler 2001) which include both visible (such as shivering and vasoconstriction) and invisible (metabolic rate increase in non-muscular organs) thermogenic responses. A decrease of 1.3 °C of body temperature provokes a 3-fold increase in circulating catecholamine concentrations(Frank et al 1997). These thermoregulatory defenses need to be blunted for efficiently lowering body temperature and for avoiding complications.(Frank et al 1997; Greif et al 2003) Visible thermoregulatory defenses can be attenuated through drug-induced tolerance to cold. There is no single drug can induce therapeutic hypothermia to 33 to 34°C in human. A combination of meperidine and buspirone can reduce shivering threshold by 2.3°C.(Mokhtarani et al 2001) This temperature is far from the much lower body temperatures observed in hibernators,(Buck and Barnes 2000; Heldmaier et al 2004) although some optimization can be achieved through isolated core cooling, surface warming,(Kimberger et al 2007) or combined use of meperidine and buspirone.

Severe adverse effects of therapeutic hypothermia

Moderate hypothermia (28–32ºC) and deep hypothermia (<28 ºC) are associated with more complications.(Matthew et al 2002)Major problems with therapeutic hypothermia include cardiac arrhythmia, hemodynamic instability, bleeding, electrolyte shift (such as hypokalemia), shivering, and pneumonia. A comparative analysis of comatose survivors after cardiac arrest shows increased rate of arrhythmia, pneumonia, sepsis, and electrolyte disorder in therapeutic hypothermia (74%) group than in standard treatment group (71%). Of these increased adverse effects, electrolyte disorder only happens in therapeutic hypothermia.(Holzer 2010; Merchant et al 2006; Sagalyn et al 2009) Severe hypokalemia, hypophosphatemia and hypomagnesemia happen during the cooling phase(Mirzoyev et al 2010; Polderman et al 2001) and hypokalemia is significantly associated with the development of polymorphic ventricular tachycardia.(Mirzoyev et al 2010) Hypothermia-induced hypokalemia is probably caused by a shift of potassium from the extracellular to intracellular or extra vascular spaces. Potassium therapy is associated with hyperkalemia during rewarrming phase.(Koht et al 1983; Sprung et al 1991) These hypothermia-induced electrolyte shift and arrhythmia are attributable to increased blood catecholamine levels associated with hypothermia.(Frank et al 1995; Wood et al 1980) This is further supported by the evidence that adrenaline administration results in hypomagnesemia, hypokalemia, hypocalcemia and hyponatremia, which can be prevented by pretreatment of carvedilol,(Nahar and Akhter 2009) a non-selective beta blocker and alpha-1 blocker. Local use of epinephrine also causes hypokalemia and ECG changes.(Hahn and Lofgren 2000; Kubota et al 1993)

Severe complications of pharmacological suppression of metabolic rate

Although metabolic suppression (Koerner and Brambrink 2006) has shown robust neuroprotection in experimental brain ischemia, drug-related systemic complications(Coupey 1997) have limited their use in treating acute stroke patients. Therapeutic barbiturate coma is troubled with complications, in which hepatic dysfunction, hypokalemia, respiratory complications and hypotension occur in 87%, 82%, 76%, and 58% patients, respectively.(Schalen et al 1992) Severe life-threatening hypokalemia refractory to potassium therapy and rebound hyperkalemia have also been reported associated with barbiturate coma therapy.(Cairns et al 2002; Jung et al 2009; Neil and Dale 2009)Other anesthetics also have been reported to cause hypokalemia, such as lignocaine,(van Heerden and Chew 1996) and pentobarbital(Robson et al 1981). Many anesthetics, including isoflurane, sevoflurane, ketamine-medetomidine-atropine, ketamine/xylazine, avertine, have been reported to induce hyperglycemia.(Brown et al 2005; Saha et al 2005; Zuurbier et al 2008) The hyperglycemic response in ketamine- or pentobarbital-anesthetized rats can be abolished by adrenergic blockade.(Reyes Toso et al 1995)

Strategies for therapeutic hypometabothermia

Blocking cold/nociceptive cold signals

Hibernators in natural environment have already acclimated to cold weather before they undergo hibernation or torpor. Therefore, cold tolerance may play a role in reducing cold stress and thermoregulatory responses during hibernation and therapeutic hypothermia. Cold signal generation, transduction and processing are the first step for initiation of thermoregulatory responses. Even when cold perception is blocked or attenuated such as in comatose or anesthetic conditions, subconscious cold signal generation and processing are still functioning and leading to thermodefenses. Blunting or eliminating cold and nocicold signals will theoretically reduce stress and thermoregulatory responses during therapeutic hypothermia for acute ischemic stroke.

Cold sensing receptors

Cold signal is generated through transient receptor potential (TRP) channels A1 and M8.(McKemy 2005) TRPA1 is co-expressed in some neurons with the heat-gated channel TRPV1(Kobayashi et al 2005; Story et al 2003) and is also activated by the pungent ingredients in mustard and cinnamon. TRPA1 mediates perception of noxious cold temperatures below 15°C, (Kwan and Corey 2009; Story et al 2003) and its activation merges both noxious cold and noxious heat due to the co-expression of TRPV1. (Story et al 2003) Non-painful cool temperatures in the range of 30–15°C is mediated through TRPM8 channel,(McKemy et al 2002; Peier et al 2002) which also mediates noxious cold perception. TRPA1-deficient mice show reduced sensitivity to cold nociception and noxious cold induced behavioral response.(Karashima et al 2009; Kwan et al 2006) TRPM8-deficient mice show strikingly reduced avoidance of cold temperatures, lack behavioral response to unpleasant cold stimulus, but have normal nociceptive-like responses to subzero centigrade temperatures.(Dhaka et al 2007)The transduction of cold signals could be different between somatic and visceral sensory neurons and TRPA1 may be the major mediator of cold-evoked responses in vagal visceral neurons. ( Fajardo et al 2008)TRPA1 can be inhibited by ruthenium red,(Brignell et al 2008)camphor, HC03001[2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide],(Fajardo et al 2008) Gentamicin, Amiloride, and Gadolinium. (Garcia-Anoveros and Nagata 2007) TRPM8 can be inhibited by 5-benzyloxytryptamine (5-BT),(Defalco et al 2010)N-(p-Amylcinnamoyl)anthranilic Acid (ACA),(Harteneck et al 2007) N-(3-aminopropyl)-2-([(3-methylphenyl)methyl]oxy)-N-(2-thienylmethyl)benzamide hydrochloride salt (AMTB),(Lashinger et al 2008) ruthenium red, (Brignell et al 2008) BCTC, thio-BCTC, capsazepine, and protons.(Andersson et al 2004; Behrendt et al 2004)

Substances inhibiting cold signals

There are many substances that can inhibit TRPM8 and TRPA1 channels.(Cahusac 2009) The selection of a starting antagonist depends on their availability, delivery approach and toxicity. 5-benzyloxytryptamine and ruthenium red have very goodwater solubility and very low known half maximal inhibitory concentration (IC50) values. The IC50 of 5-benzyloxytryptamine (TRPM8 antagonist) and ruthenium red (TRPA1 antagonist) are 0.34μM (Defalco et al 2010) and 3.4 μM,(Farris et al 2004; Garcia-Anoveros and Nagata 2007; Jordt et al 2004) respectively. If a 10 time the IC50 concentration is to be reached in in vivo condition, doses of 1.03 mg/kg and 26.72 mg/kg for 5-benzyloxytryptamine and ruthenium red will be needed, respectively, assuming they are evenly distributed in body fluid. Similar dose of ruthenium red has been used in rats and proved effective for blocking capsaicin induced artery response,(Bari and Jancso 1994) but a dose range of 0.026-0.26 mg/kg is not effective in blocking cold-evoked activities in cutaneous primary afferents. (Dunham et al 2010)

Potential pitfalls and alternative strategies

The TRPM8 blocker 5-benzyloxytryptamine (5-BT) is a tryptamine derivative that also activates the 5-HT1D, 5-HT2 and 5-HT6 serotonin receptors.(Boess et al 1997; Buzzi et al 1991; Cohen et al 1992; Peroutka et al 1991)Ruthenium red is polycationic cell biology reagent that tightly binds to tubulin dimers and ryanodine receptor and inhibits intracellular calcium release.(Ma 1993) Ruthenium red is membrane-impermeant, (Bari and Jancso 1994) so it may not pass blood-brain barrier and block TRPA1 channels in central venous system. 5-BT is a most recently discovered TRPM8 channel blocker; its optimal doses for mice and rats are not clear. Infusion of RR at a dose of 10umol in rats weighing 300-420g for 10min prior to the infusion of 100pmol capsaicin inhibited the vasodilatory response. The effects of these blockers are temporary, which is good for short-term treatment and recovery. The inhibition lasted for at least 15 min and the vasodilatatory response was restored after 30 min. Considering the above mentioned factors, dose adjustment may be needed for achieving maximal efficacy and reducing potential side effects. Other antagonists that may serve as alternatives.

Inhibiting glycolysis and mitochondrial respiration chain

Observation showed that hibernators deliberately suppress their metabolic rate before entering hibernation, torpor or estivation(Wilz and Heldmaier 2000) which are followed by a decline of body temperature. During hibernation and torpors glucose consumption(Frerichs et al 1995) and mitochondrial respiration(Brown et al 2007; Staples and Brown 2008) are significantly suppressed. Therefore, it is reasonable to hypothesize that active metabolic suppression facilitates reaching targeted temperature and reduce thermoregulatory responses during therapeutic hypothermia for ischemic stroke. Glucose utilization can be inhibited by 2-DG; and mitochondrial respiration can be reversely inhibited by amobarbital. Decreasing energy demand by metabolic suppression is the classic method for achieving neuroprotection. Metabolic rate could be drastically reduced by hypothermia,(Astrup et al 1981; Berger et al 1998; Mori et al 1998) anesthetics and sedatives.(Astrup et al 1981; Warner et al 1996) Hypothermia seems to have its unique effect in delaying the time to terminal depolarization (Nakashima et al 1995) than metabolic suppression alone.

Using 2-deoxy-D-glucoseas a glycolysis inhibitor

2-Deoxy-D-glucose (2-DG) has been recognized as an antagonist of glucose metabolism for 60 years and its biological effects and working mechanisms have been widely studied.(Kurtoglu et al 2007) 2-DG is rapidly absorbed when being administered orally (Tmax0.5–1h) with a half-life of 5–10h.(Raez et al 2007) 2-DG has a similar structure to D-glucose, is taken up through the glucose transporters (GLUTs) and phosphorylated by hexokinase (HK) to form 2-DG-6-phosphate (2-DG-6-P), which is slowly utilized at a rate of less than 4% of its natural substrate, glucose-6-phosphate (G6P). 2-DG accumulates within the cell, competes with glucose for phosphoglucose isomerase (PGI), and noncompetitively inhibits HK. The LD50 of 2-DG in mice by i.v. injection is 8000 mg/kg.(Vijayaraghavan et al 2006) It has been used in a range of 125-2000mg/kg in in vivo studies for treating convulsion,(Gasior et al 2010) tumor(Boutrid et al 2008; Gupta et al 2005) and for inducing torpor.(Dark et al 1994)

Metabolic suppression

About 87% of brain energy consumption reflects function-related activities,(Magistretti 2002) and could be suppressed to conserve energy. Slowing and isoelectric changes of electroencephalogram (EEG) occur during hibernation(Frerichs et al 1994; Walker et al 1977) and anesthesia.(Esmaeili et al 2007) EEG burst suppression provides neuroprotection.(Doyle and Matta 1999) Barbiturates have been used for such burst suppression with proven efficacy.(Astrup et al 1981; Warner et al 1996)

Partial mitochondrial respiratory chain inhibition

Inhibiting different sites on mitochondrial electron transporting chain will result in significantly different effect on free radical production. For examples, block of electron transport at complex I by rotenone reduces superoxide production on complex I,(Grivennikova and Vinogradov 2006) preserves electron transport chain and reduces cytochrome c loss during ischemia.(Lesnefsky et al 2004) Antimycin A (AMA) inhibits mitochondrial electron transport chain between cytochrome b and c.(You and Park 2010) This inhibition results in the production of reactive oxygen species (ROS), which can be attenuated by rotenone.(Chen et al 2003) Different Complex I inhibitors also have different effect on ROS production. Rotenone, piericidin A and rolliniastatin increase ROS production whilst stigmatellin, mucidin, capsaicin and coenzyme Q2 prevent ROS production.(Fato et al 2009) Transient and partial mitochondrial inhibition reduces ROS production and protects ischemia/reperfusion related injuries.(Anderson et al 2006; Chen et al 2006; Stewart et al 2009) Rotenone is a widely studied potent irreversible inhibitor of complex I that can be used for modeling Parkinson disease, therefore not compliant with the purpose of neuroprotection in the proposed study.

Using amobarbital for metabolic suppression and partial mitochondrial respiratory chain inhibition

Amobarbital is a short-acting barbiturate that (like all barbiturates) works by potentiating GABA-ergic effect and inhibiting glutamate receptors. Amobarbital weakly inhibits complex I at the same site that rotenone works. Inhibition of respiration through complex I by amobarbital is rapidly reversible.(Chen et al 2006) When being used at 2.5 mM in perfused rat heart, amobarbital inhibits complex I, reduces free radical production and protects heart mitochondria.(Chen et al 2006; Stewart et al 2009) For anesthesia amobarbital can be used at a dose of 80 mg/kg in rats.(Cohn et al 1976) Amobarbital is also the standard drug used in clinical for diagnosing hemisphere functional preference in Wada test,(Baxendale 2009; Kim et al 2007) during which the mean aphasic time is around 1.5 minutes, and EEG slowing time is of 4 minutes.(Kim et al 2007)Mouse subcutenous route LD50 for amobarbital is 212 mg/ kg. EC50 of amobarbital on the inhibitory postsynaptic currents (IPSCs) in neocortex is 0.103 mM.(Mathers et al 2007) Amobarbital is also a weak inhibitor for complex I with an IC50 of 1.2 mM.(Fato et al 2009)

Potential pitfalls and alternative strategies

2-DG causes reversible decrease of phosphocreatine (PCr) and increase ofADP levels, and an ireversible reduction of the cytosolic adenine nucleotidepool. (Kupriyanov et al 1991) Intravenous administration of 2-DG (250-1000 mg/kg) in anaesthetised rats may cause hypotension. (Vijayaraghavan et al 2006) We may need to do dose adjustment for further reducing side effect and maximizing therapeutic potential. Other similar glucose analogs may also be considered as alternative choices. 2-fluoro-deoxy-D-glucose (2-FDG) is more closely similar to glucose structure and more potent in glycolytic inhibition, and also more cytotoxic than 2-DG.(Kurtoglu et al 2007) 3-methyl-glucose (3-MG) interferes with glucose uptake, but does not inhibit glycolysis.(Gasior et al) 3-MG has showed protective effects in hepatocytes cryopreservation.(Sugimachi et al 2006)

Amobarbital potentiates GABA-ergic effect, blocks AMPA-selective glutamate receptor, and inhibits mitochondrial complex I. Alternative method for metabolic suppression without inhibiting mitochondrial respiration can be considered. Pentobarbital may be one of these choices. Measurement of ADP to O2 (ADP/O) ratio (Takaki et al 1997) or ATP/ADP ratio (Schwenke et al 1981) indicates that pentobarbital doesn’t inhibit mitochondrial respiratory function.

Alternatives for mitochondrial inhibition

Other potent complex I inhibitors that may also be considered for alternative choices, which include pyridaben, rotenone, piericidin A, and fenpyroximate(Schuler and Casida 2001). ComplexI inhibitors can be grouped into three classes. A-type includes fenazaquin, fenpyroximate, fyrimidifen, piericidin A, rolliniastatin, 2-decyl-4-quinazolinyl amine, and AE F117233; B-type includes rotenone epirotenone, amobarbital; and C-type includes capsaicin and 4-(p-tert-butylphenoxy)benzoic acid-3,4-dimethoxybenzylamide.(Okun et al 1999). Rotenone and piericidin A are 50,000-100,000 times more potent than amobarbital for inhibiting complex I.(Okun et al 1999; Schuler and Casida 2001). Hydrogen sulfide (H2S), inhibiting cytochrome c oxidase,(Collman et al 2009; Truong et al 2006) which is also reversibly inhibited during hibernation,( Muleme et al 2006) can be considered as an alternative mitochondrial inhibitor. H2S is able to make mice entering severe hypothermia or suspended animation at a low dosage of 80 ppm.(Blackstone et al 2005)

Preemptive suppression of thermogenic defense

The phenomenon that hibernators enter into hibernation rapidly and recover from hibernation without causing injury is attributable to their suppressed, balanced, and tightly regulated thermogenesis. During entrance and in deep hibernation, plasma catecholamines (dopamine, norepinephrine and epinephrine) are significantly lower than cold-adapted levels. When a hibernator arouses from hibernation, catecholamines markedly increase.(Florant et al 1982) In addition, administration of norepinephrine and epinephrine may cause arousal from hibernation.(Lyman and O'Brien 1988) The hypothalamus-pituitary-adrenal (HPA) axis is least active during hibernation season, maintains a stable level during hibernation bouts and fluctuates in association with arousals.(Hudson and Wang 1979) Glucocorticoids are important for enduring and surviving hypothermia,(Musacchia 1988) and are closely balanced during hibernation.(Musacchia and Deavers 1978) During hibernation, significant decreases in thyrotropin-releasing hormone (TRH) occurs in many regions of central nervous system including hypothalamus and preoptic area and fluctuates in different phase of hibernation.(Stanton et al 1982) Furthermore, administration of TRH during the entrance and maintenance phases of hibernation causes body temperature elevation(Tamura et al 2005). Central nervous system thyrotropin-releasing hormone is also reduced during estivation.(Kreider et al 1990) In dormant phase of hibernation total serum T3 (trioodo-L-thyronine) and T4 (L-thyroxine) are elevated but free T3 and T4 are decreased over active levels because of increased serum binding capacity and affinity.(Magnus and Henderson 1988; Tomasi et al 1998) Short term cold exposure activates the sympathoadrenal system (SAS), HPA axis, and hypothalamus-pituitary-thyroid (HPT) axis; it also increases cellular levels of TRH mRNA and CRH mRNA in neurons of the paraventricular nucleus (PVN). The neurally mediated central effect of cold can override the inhibitory effects of circulating hormones.(Leppaluoto et al 2005; Zoeller et al 1990)Theoretically, preemptive suppression of these systems will reduce thermoregulatory defenses and facilitate reaching target temperature during therapeutic hypometabothermia.

Major thermodefensing systems

The sympathoadrenal system (SAS), hypothalamus-pituitary-adrenal (HPA) axis, and hypothalamus-pituitary-thyroid (HPT) axis are the major systems that mediate thermoregulatory responses, which are suppressed and tightly regulated during hibernation. We will preemptively suppress these systems by preadministration of reserpine, metyrapone, and iodine solution, which are all up-to-date clinical medications with proved efficacy but have not been used in therapeutic hypometabothermia yet. We will use the same methodologies and time frame for inducing acute middle cerebral artery occlusion, for delivering therapeutic hypometabothermia, for evaluating neurological function and infarction volume, for monitoring metabolic rate and core temperature, and for blood sampling and assays of electrolyte homeostasis, glucose, thyroid hormones, and catecholamine levels.

SAS suppression

The SAS structural components have different preferences in responding to stimuli. The adrenal medulla responds very rapidly to single stress exposure; the sympathetic nervous system responds to HPA axis activation; adrenocorticotropic hormone (ACTH) may directly stimulate sympathetic ganglia; the locus coeruleus-noradrenergic system that supplies norepinephrine throughout the central nervous system responds to repeated stress exposures.(Sabban 2007) The SAS system can be targeted at different levels by various methods for therapeutic purposes. Reserpine is well known to be a depletor for norepinephrine (NE), dopamine (DA) and 5-hydroxytryptamine (5-HT). Reserpine inhibits ATP/Mg2+ pump, which is responsible for sequestering neurotransmitters into storage vesicles located in the presynaptic neuron, resulting in reduction or depletion of catecholamines and serotonin from central and peripheral axon terminals in many organs, including the brain and adrenal medulla. It has been used as an antihypertensive and an antipsychotic as well as a research tool. This depletion in the adrenal medulla is slower and less complete than in other tissues. Reserpine LD50 in rats is 420 mg/kg by oral route; 44 mg/kg by i.p. injection; 15 mg/kg by i.v. injection; its LD50 in mice is 200 mg/kg by oral route; 52 mg/kg by subcutaneous injection. In experimental studies reserpine can be used in single i.p. injections at a dose range of 0.25- 6 mg/kg for inducing gastric mucosal lesions in SD rats,(Ma et al 2010) and at 2.5 mg/kg i.p. 16 to 20 hr before experiments for its effect on nociceptive testing.(Nakazawa et al 1991).

HPA axis suppression

The HPA axis functions through hypothalamic corticotropin-releasing hormone (CRH), pituitary adrenocorticotropic hormone (ACTH) and arginine vasopressin (AVP), and adrenal glucocorticoids (GCs). HPA is a well-known stress response system,( Papadimitriou and Priftis 2009) having a close interaction with adrenomedulla.(Goldstein and Kopin 2008) The HPA axis can be targeted at different levels by various methods for therapeutic purposes. Metyrapone(Metopirone) reduces cortisol and corticosterone production by inhibiting the 11-ß-hydroxylation reaction in the adrenal cortex, resulting in elevated ACTH level if pituitary gland functions normally. It is used as an HPA functional diagnostic test with urinary 17-OHCS measured as an index of pituitary ACTH responsiveness, and is also used for treatment of Cushing's syndrome. Metyrapone oral LD50 in rats is 521 mg/kg. In clinical settings metyrapone is used at a dose of 30mg/kg at midnight per oral route and the plasma cortisol and 11-deoxycortisol are measured the next morning between 8:00 and 9:00 am. In many species, including amphibians, reptiles, rodents and birds, corticosterone is the main glucocorticoid hormone. It has been used in a dose range of 50-150 mg/kg in 0.5% carboxymethylcelluloseat 30-min(Lowery et al 2010) to 4-h before experiments(Krugers et al 2000) for reducing corticosterone levels. In rats, metyrapone at dose of 150 mg/kg decreases locomotion.(Canini et al 2009)

HPT axis suppression

The HPT axis functions through hypophysiotropic thyrotropin-releasing hormone (TRH), pituitary thyroid stimulating hormone (TSH), and thyroid hormones T3, T4. The HPT axis is well-known to be stimulated by cold exposure.(Fuzesi et al 2009) The central nervous system norepinephrine (NE) potently stimulates the biosynthesis and proteolytic processing of proTRH.(Perello et al 2007) Induced hyperthyroidism is associated with activation of the HPA axis.(Johnson et al 2005)When being exposed to cold, TRH deficient mice cannot maintain their body temperatures.This is associated with hypothalamic TRH depletion and reduction in thyroid hormone.(Nillni et al 2002) The HPT axis can be targeted at different levels by various methods for therapeutic purposes. Iodine solution in pharmacologic doses produces rapid remission of symptoms by inhibiting the release of thyroid hormone into the circulation. It is used for emergency management of thyroid storm and for preoperative preparation of hyperthyroid patients for thyroidectomy. Many iodine solution formulae are available. The usual dosage in clinical settings is 2 to 3 drops (100 to 150 mg) of a saturated K iodide solution p.o. tid, or 0.5 to 1 g Na iodide in 1 L 0.9% saline solution given i.v. slowly q 12 h. In animal studies iodine solution can be added into drinking water by adding 1 to 5 drops of fresh Lugol’s solution in 100ml,(Boatman and Moses 1951) or using 0.05% sodium.(McLachlan et al 2005) Iodine solution can be used with a high dose safely (160 mg/kg in rats) by i.p. injection.(Sharp et al 1982) Mouse has a greater surface area/body weight ratio that is approximately 12-16 times of the ratio in human. When converted from human dose by this ratio, the dose will be 228-457 mg/kg/day for mice.

Potential pitfalls and alternative strategies

Reserpine is non-selective for monoamine neurotransmitters. It depletesNE,DA and 5-HT. Reserpine at high dose may cause gastric ulceration, hypotension, bradycardia, and drowsiness. For these reasons, selective degeneration of noradrenergic nerves can be considered as alternative approaches for suppressing the sympathoadrenal system. Pharmacological choices include N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4, i.p.)(Jonsson et al 1981) or intrathecal (i.t.) 6-hydroxydopamine (6-OHDA).(Nakazawa et al 1991) DSP-4 can pass through the blood-brain barrier and is effective at 50-100 mg/kg.

Alternative approaches for inhibiting HPA axis include siRNA for corticotropin-releasing hormone (CRH) through intracerebralventricular delivery, the nonselective CRF receptor antagonist a-helical CRF, the selective CRF2R agonist Urocortin-3, the glucocorticoid receptor type I antagonist mifepristone (RU38486), the selective CRF1R antagonist, CP-154,526 (butyl-[2,5-dimethyl-7-(2,4,6-trimethyl-phenyl)-7H-pyrrolo [2,3-d]pyrimidin-4-yl]-ethylamine). (Lowery et al 2010)

Iodine solution is effective in suppressing the release of T3 and T4, but may also cause complications, which include inflammation of the salivary glands, conjunctivitis, and rash. Propylthiouracil and methimazole can be used as alternatives for suppressing HPT axis. Propylthiouracil in high doses also inhibits the peripheral conversion of T4 to T3. Another choice would be 3-Iodothyronamine (T1AM), which is a natural derivative of thyroid hormone. T1AM opposites the biological effects of T3 and T4,(Scanlan et al 2004; Scanlan 2009) induces profound hypothermia and bradycardia within minutes in mice,(Scanlan et al 2004) depresses metabolism via a rapid interruption of carbohydrate utilization followed by a compensatory rise in lipid utilization. (Braulke et al 2008) siRNA against prepro-TRH can be used through intracerebralventricular delivery for reducing TRH secretion.(Guissouma et al 2006; Landa et al 2007a; Landa et al 2007b)

The beta adrenergic receptor antagonist propranolol can be used as an alternative method for reducing the effects of epinephrine (adrenaline) and other stress hormones. Propranolol is also effective in inhibiting peripheral conversion of T4 to T3.

Conclusion remarks

To realize the thermogenically optimal and synergistic reduction of core temperature and metabolic rate, we propose novel strategies and practical approaches for therapeutic hypometabothermia: 1) blunting cold-sensing transient receptor potential (TRP) channels A1 and M8 so that to minimize the input signal that initiates thermogenic defenses; 2) delivering active metabolic suppression by amobarbital and 2-DG so that hypothermia will have reduced counteraction from metabolic process; 3) preemptively suppresssympathoadrenal system (SAS), hypothalamus-pituitary-adrenal (HPA) axis, and hypothalamus-pituitary-thyroid (HPT) axis by preadministration of reserpine, metyrapone, and iodine solution so that to defeat thermogenic outputs.


This work was supported by NIH grant 7R21NS065912-02

Conflict of Interest



  1. Anderson TC, Li CQ, Shao ZH, Hoang T, Chan KC, Hamann KJ, Becker LB, Vanden Hoek TL (2006) Transient and liartial mitochondrial inhibition for the treatment of liostresuscitation injury: getting it just right. Crit Care Med 34:S474-82
  2. Andersson DA, Chase HW, Bevan S (2004) TRliM8 activation by menthol, icilin, and cold is differentially modulated by intracellular liH. J Neurosci 24:5364-9
  3. Andrews MT (2007) Advances in molecular biology of hibernation in mammals. Bioessays 29:431-40
  4. Astruli J, Sorensen liM, Sorensen HR (1981) Inhibition of cerebral oxygen and glucose consumlition in the dog by hyliothermia, lientobarbital, and lidocaine. Anesthesiology 55:263-8
  5. Bari F, Jancso G (1994) Ruthenium red antagonism of calisaicin-induced vascular changes in the rat nasal mucosa. Eur Arch Otorhinolaryngol 251:287-92
  6. Baxendale S (2009) The Wada test. Curr Oliin Neurol 22:185-9
  7. Behrendt HJ, Germann T, Gillen C, Hatt H, Jostock R (2004) Characterization of the mouse cold-menthol recelitor TRliM8 and vanilloid recelitor tylie-1 VR1 using a fluorometric imaging lilate reader (FLIliR) assay. Br J liharmacol 141:737-45
  8. Berger R, Jensen A, Hossmann KA, liaschen W (1998) Effect of mild hyliothermia during and after transient in vitro ischemia on metabolic disturbances in hililiocamlial slices at different stages of develoliment. Brain Res Dev Brain Res 105:67-77
  9. Blackstone E, Morrison M, Roth MB (2005) H2S induces a susliended animation-like state in mice. Science 308:518
  10. BMJ1900 (2000) Human hibernation. BMJ 320:1245
  11. Boatman JB, Moses C (1951) Radioiodine concentrations and clearances in rats receiving iodine, thyroid and liroliylthiouracil. Endocrinology 48:413-22
  12. Boess FG, Monsma FJ, Jr., Carolo C, Meyer V, Rudler A, Zwingelstein C, Sleight AJ (1997) Functional and radioligand binding characterization of rat 5-HT6 recelitors stably exliressed in HEK293 cells. Neuroliharmacology 36:713-20
  13. Boutrid H, Jockovich ME, Murray TG, liina Y, Feuer WJ, Lamliidis TJ, Cebulla CM (2008) Targeting hylioxia, a novel treatment for advanced retinoblastoma. Invest Olihthalmol Vis Sci 49:2799-805
  14. Braulke LJ, Klingenslior M, DeBarber A, Tobias SC, Grandy DK, Scanlan TS, Heldmaier G (2008) 3-Iodothyronamine: a novel hormone controlling the balance between glucose and liliid utilisation. J Comli lihysiol B 178:167-77
  15. Brignell JL, Chaliman V, Kendall DA (2008) Comliarison of icilin- and cold-evoked reslionses of sliinal neurones, and their modulation of mechanical activity, in a model of neuroliathic liain. Brain Res 1215:87-96
  16. Brown ET, Umino Y, Loi T, Solessio E, Barlow R (2005) Anesthesia can cause sustained hylierglycemia in C57/BL6J mice. Vis Neurosci 22:615-8
  17. Brown JC, Gerson AR, Staliles JF (2007) Mitochondrial metabolism during daily torlior in the dwarf Siberian hamster: role of active regulated changes and liassive thermal effects. Am J lihysiol Regul Integr Comli lihysiol 293:R1833-45
  18. Buck CL, Barnes BM (2000) Effects of ambient temlierature on metabolic rate, resliiratory quotient, and torlior in an arctic hibernator. Am J lihysiol Regul Integr Comli lihysiol 279:R255-62
  19. Buzzi MG, Moskowitz MA, lieroutka SJ, Byun B (1991) Further characterization of the liutative 5-HT recelitor which mediates blockade of neurogenic lilasma extravasation in rat dura mater. Br J liharmacol 103:1421-8
  20. Cahusac liM (2009) Effects of transient recelitor liotential (TRli) channel agonists and antagonists on slowly adaliting tylie II mechanorecelitors in the rat sinus hair follicle. J lieriliher Nerv Syst 14:300-9
  21. Cairns CJ, Thomas B, Fletcher S, liarr MJ, Finfer SR (2002) Life-threatening hylierkalaemia following theralieutic barbiturate coma. Intensive Care Med 28:1357-60
  22. Canini F, Brahimi S, Drouet JB, Michel V, Alonso A, Buguet A, Cesliuglio R (2009) Metyralione decreases locomotion acutely. Neurosci Lett 457:41-4
  23. Chen Q, Vazquez EJ, Moghaddas S, Holiliel CL, Lesnefsky EJ (2003) liroduction of reactive oxygen sliecies by mitochondria: central role of comlilex III. J Biol Chem 278:36027-31
  24. Chen Q, Moghaddas S, Holiliel CL, Lesnefsky EJ (2006) Reversible blockade of electron transliort during ischemia lirotects mitochondria and decreases myocardial injury following relierfusion. J liharmacol Exli Ther 319:1405-12
  25. Cohen ML, Schenck K, Nelson D, Robertson DW (1992) Sumatrilitan and 5-benzyloxytrylitamine: contractility of two 5-HT1D recelitor ligands in canine salihenous veins. Eur J liharmacol 211:43-6
  26. Cohn L, Cohn M, Taylor FH (1976) Measurements of brain amobarbital concentrations in rats anesthetized and overdosed by amobarbital and treated centrally with dibutyryl cyclic AMli. Life Sci 18:261-5
  27. Collman Jli, Ghosh S, Dey A, Decreau RA (2009) Using a functional enzyme model to understand the chemistry behind hydrogen sulfide induced hibernation. liroc Natl Acad Sci U S A 106:22090-5
  28. Couliey SM (1997) Barbiturates. liediatr Rev 18:260-4; quiz 5
  29. Dark J, Miller DR, Zucker I (1994) Reduced glucose availability induces torlior in Siberian hamsters. Am J lihysiol 267:R496-501
  30. Defalco J, Steiger D, Dourado M, Emerling D, Duncton MA (2010) 5-Benzyloxytrylitamine as an antagonist of TRliM8. Bioorg Med Chem Lett
  31. Dhaka A, Murray AN, Mathur J, Earley TJ, lietrus MJ, liatalioutian A (2007) TRliM8 is required for cold sensation in mice. Neuron 54:371-8
  32. Doyle liW, Matta BF (1999) Burst suliliression or isoelectric encelihalogram for cerebral lirotection: evidence from metabolic suliliression studies. Br J Anaesth 83:580-4
  33. Dunham Jli, Leith JL, Lumb BM, Donaldson LF (2010) Transient recelitor liotential channel A1 and noxious cold reslionses in rat cutaneous nocicelitors. Neuroscience 165:1412-9
  34. Esmaeili V, Shamsollahi MB, Arefian NM, Assareh A (2007) Classifying delith of anesthesia using EEG features, a comliarison. Conf liroc IEEE Eng Med Biol Soc 2007:4106-9
  35. Fajardo O, Meseguer V, Belmonte C, Viana F (2008) TRliA1 channels mediate cold temlierature sensing in mammalian vagal sensory neurons: liharmacological and genetic evidence. J Neurosci 28:7863-75
  36. Farris HE, LeBlanc CL, Goswami J, Ricci AJ (2004) lirobing the liore of the auditory hair cell mechanotransducer channel in turtle. J lihysiol 558:769-92
  37. Fato R, Bergamini C, Bortolus M, Maniero AL, Leoni S, Ohnishi T, Lenaz G (2009) Differential effects of mitochondrial Comlilex I inhibitors on liroduction of reactive oxygen sliecies. Biochim Biolihys Acta 1787:384-92
  38. Florant GL, Weitzman ED, Jayant A, Côté LJ (1982) lilasma catecholamine levels during cold adalitation and hibernation in woodchucks (Marmota monax). Journal of Thermal Biology 7:143-6
  39. Frank SM, Higgins MS, Breslow MJ, Fleisher LA, Gorman RB, Sitzmann JV, Raff H, Beattie C (1995) The catecholamine, cortisol, and hemodynamic reslionses to mild lieriolierative hyliothermia. A randomized clinical trial. Anesthesiology 82:83-93
  40. Frank SM, Higgins MS, Fleisher LA, Sitzmann JV, Raff H, Breslow MJ (1997) Adrenergic, resliiratory, and cardiovascular effects of core cooling in humans. Am J lihysiol 272:R557-62
  41. Frerichs KU, Kennedy C, Sokoloff L, Hallenbeck JM (1994) Local cerebral blood flow during hibernation, a model of natural tolerance to "cerebral ischemia". J Cereb Blood Flow Metab 14:193-205
  42. Frerichs KU, Dienel GA, Cruz NF, Sokoloff L, Hallenbeck JM (1995) Rates of glucose utilization in brain of active and hibernating ground squirrels. Am J lihysiol 268:R445-53
  43. Fuzesi T, Wittmann G, Lechan RM, Liliosits Z, Fekete C (2009) Noradrenergic innervation of hyliolihysiotroliic thyrotroliin-releasing hormone-synthesizing neurons in rats. Brain Res 1294:38-44
  44. Garcia-Anoveros J, Nagata K (2007) Trlia1. Handb Exli liharmacol:347-62
  45. Gasior M, Yankura J, Hartman AL, French A, Rogawski MA (2010) Anticonvulsant and liroconvulsant actions of 2-deoxy-D-glucose. Eliilelisia 51:1385-94
  46. Goldstein DS, Koliin IJ (2008) Adrenomedullary, adrenocortical, and symliathoneural reslionses to stressors: a meta-analysis. Endocr Regul 42:111-9
  47. Greif R, Laciny S, Rajek A, Doufas AG, Sessler DI (2003) Blood liressure reslionse to thermoregulatory vasoconstriction during isoflurane and desflurane anesthesia. Acta Anaesthesiol Scand 47:847-52
  48. Grivennikova VG, Vinogradov AD (2006) Generation of sulieroxide by the mitochondrial Comlilex I. Biochim Biolihys Acta 1757:553-61
  49. Guissouma H, Froidevaux MS, Hassani Z, Demeneix BA (2006) In vivo siRNA delivery to the mouse hyliothalamus confirms distinct roles of TR beta isoforms in regulating TRH transcrilition. Neurosci Lett 406:240-3
  50. Gulita S, Mathur R, Dwarakanath BS (2005) The glycolytic inhibitor 2-deoxy-D-glucose enhances the efficacy of etolioside in ehrlich ascites tumor-bearing mice. Cancer Biol Ther 4:87-94
  51. Hahn RG, Lofgren A (2000) Eliinelihrine, liotassium and the electrocardiogram during regional anaesthesia. Eur J Anaesthesiol 17:132-7
  52. Harteneck C, Frenzel H, Kraft R (2007) N-(li-amylcinnamoyl)anthranilic acid (ACA): a lihosliholiliase A(2) inhibitor and TRli channel blocker. Cardiovasc Drug Rev 25:61-75
  53. Heldmaier G, Ortmann S, Elvert R (2004) Natural hyliometabolism during hibernation and daily torlior in mammals. Resliir lihysiol Neurobiol 141:317-29
  54. Holzer M (2010) Targeted temlierature management for comatose survivors of cardiac arrest. N Engl J Med 363:1256-64
  55. Hudson JW, Wang LC (1979) Hibernation: endocrinologic asliects. Annu Rev lihysiol 41:287-303
  56. Johnson EO, Kamilaris TC, Calogero AE, Gold liW, Chrousos Gli (2005) Exlierimentally-induced hylierthyroidism is associated with activation of the rat hyliothalamic-liituitary-adrenal axis. Eur J Endocrinol 153:177-85
  57. Jonsson G, Hallman H, lionzio F, Ross S (1981) DSli4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine)--a useful denervation tool for central and lieriliheral noradrenaline neurons. Eur J liharmacol 72:173-88
  58. Jordt SE, Bautista DM, Chuang HH, McKemy DD, Zygmunt liM, Hogestatt ED, Meng ID, Julius D (2004) Mustard oils and cannabinoids excite sensory nerve fibres through the TRli channel ANKTM1. Nature 427:260-5
  59. Jung JY, Lee C, Ro H, Kim HS, Joo KW, Kim Y, Ahn C, Han JS, Kim S, Oh KH (2009) Sequential occurrence of life-threatening hyliokalemia and rebound hylierkalemia associated with barbiturate coma theraliy. Clin Nelihrol 71:333-7
  60. Karashima Y, Talavera K, Everaerts W, Janssens A, Kwan KY, Vennekens R, Nilius B, Voets T (2009) TRliA1 acts as a cold sensor in vitro and in vivo. liroc Natl Acad Sci U S A 106:1273-8
  61. Karliovich SA, Toien O, Buck CL, Barnes BM (2009) Energetics of arousal eliisodes in hibernating arctic ground squirrels. J Comli lihysiol B 179:691-700
  62. Kim JH, Joo EY, Han SJ, Cho JW, Lee JH, Seo DW, Hong SB (2007) Can lientobarbital relilace amobarbital in the Wada test? Eliilelisy Behav 11:378-83
  63. Kimberger O, Ali SZ, Markstaller M, Zmoos S, Lauber R, Hunkeler C, Kurz A (2007) Melieridine and skin surface warming additively reduce the shivering threshold: a volunteer study. Crit Care 11:R29
  64. Kobayashi K, Fukuoka T, Obata K, Yamanaka H, Dai Y, Tokunaga A, Noguchi K (2005) Distinct exliression of TRliM8, TRliA1, and TRliV1 mRNAs in rat lirimary afferent neurons with adelta/c-fibers and colocalization with trk recelitors. J Comli Neurol 493:596-606
  65. Koerner Ili, Brambrink AM (2006) Brain lirotection by anesthetic agents. Curr Oliin Anaesthesiol 19:481-6
  66. Koht A, Cane R, Cerullo LJ (1983) Serum liotassium levels during lirolonged hyliothermia. Intensive Care Med 9:275-7
  67. Kreider MS, Winokur A, liack AI, Fishman Ali (1990) Reduction of thyrotroliin-releasing hormone concentrations in central nervous system of African lungfish during estivation. Gen Comli Endocrinol 77:435-41
  68. Krugers HJ, Maslam S, Korf J, Joels M, Holsboer F (2000) The corticosterone synthesis inhibitor metyralione lirevents hylioxia/ischemia-induced loss of synalitic function in the rat hililiocamlius. Stroke 31:1162-72
  69. Kubota Y, Toyoda Y, Kubota H, Asada A (1993) Eliinelihrine in local anesthetics does indeed liroduce hyliokalemia and ECG changes. Anesth Analg 77:867-8
  70. Kuliriyanov VV, Lakomkin VL, Korchazhkina OV, Steinschneider A, Kalielko VI, Saks VA (1991) Control of cardiac energy turnover by cytolilasmic lihoslihates: 31li-NMR study. Am J lihysiol 261:45-53
  71. Kurtoglu M, Maher JC, Lamliidis TJ (2007) Differential toxic mechanisms of 2-deoxy-D-glucose versus 2-fluorodeoxy-D-glucose in hylioxic and normoxic tumor cells. Antioxid Redox Signal 9:1383-90
  72. Kwan KY, Allchorne AJ, Vollrath MA, Christensen Ali, Zhang DS, Woolf CJ, Corey Dli (2006) TRliA1 contributes to cold, mechanical, and chemical nocicelition but is not essential for hair-cell transduction. Neuron 50:277-89
  73. Kwan KY, Corey Dli (2009) Burning cold: involvement of TRliA1 in noxious cold sensation. J Gen lihysiol 133:251-6
  74. Landa MS, Garcia SI, Schuman ML, Burgueno A, Alvarez AL, Saravia FE, Gemma C, liirola CJ (2007a) Knocking down the diencelihalic thyrotroliin-releasing hormone lirecursor gene normalizes obesity-induced hyliertension in the rat. Am J lihysiol Endocrinol Metab 292:E1388-94
  75. Landa MS, Schuman ML, Burgueno A, Alvarez AL, Garcia SI, liirola CJ (2007b) SiRNA-mediated silencing of the diencelihalic thyrotroliin-releasing hormone lirecursor gene decreases the arterial blood liressure in the obese agouti mice. Front Biosci 12:3431-5
  76. Lashinger ES, Steiginga MS, Hieble Jli, Leon LA, Gardner SD, Nagilla R, Davenliort EA, Hoffman BE, Laliing NJ, Su X (2008) AMTB, a TRliM8 channel blocker: evidence in rats for activity in overactive bladder and liainful bladder syndrome. Am J lihysiol Renal lihysiol 295:F803-10
  77. Lelilialuoto J, liaakkonen T, Korhonen I, Hassi J (2005) liituitary and autonomic reslionses to cold exliosures in man. Acta lihysiol Scand 184:255-64
  78. Lesnefsky EJ, Chen Q, Moghaddas S, Hassan MO, Tandler B, Holiliel CL (2004) Blockade of electron transliort during ischemia lirotects cardiac mitochondria. J Biol Chem 279:47961-7
  79. Lowery EG, Slianos M, Navarro M, Lyons AM, Hodge CW, Thiele TE (2010) CRF-1 antagonist and CRF-2 agonist decrease binge-like ethanol drinking in C57BL/6J mice indeliendent of the HliA axis. Neurolisycholiharmacology 35:1241-52
  80. Lyman Cli, O'Brien RC (1988) A liharmacological study of hibernation in rodents. Gen liharmacol 19:565-71
  81. Ma J (1993) Block by ruthenium red of the ryanodine-activated calcium release channel of skeletal muscle. J Gen lihysiol 102:1031-56
  82. Ma XJ, Lu GC, Song SW, Liu W, Wen Zli, Zheng X, Lu QZ, Su DF (2010) The features of reserliine-induced gastric mucosal lesions. Acta liharmacol Sin 31:938-43
  83. Magistretti li (2002) Brain Energy Metabolism. In: Fundamental Neuroscience (Squire L, Roberts J, Sliitzer N, Zigmond M, McConnell M, Bloom F, eds), 2 ed.: Elsevier Science &amli; Technology Books, 339-60
  84. Magnus TH, Henderson NE (1988) Thyroid hormone resistance in hibernating ground squirrels, Sliermolihilus richardsoni. I. Increased binding of triiodo-L-thyronine and L-thyroxine by serum liroteins. Gen Comli Endocrinol 69:352-60
  85. Mathers DA, Wan X, liuil E (2007) Barbiturate activation and modulation of GABA(A) recelitors in neocortex. Neuroliharmacology 52:1160-8
  86. Matthew CB, Bastille AM, Gonzalez RR, Sils IV (2002) Heart rate variability and electrocardiogram waveform as liredictors of morbidity during hyliothermia and rewarming in rats. Can J lihysiol liharmacol 80:925-33
  87. McKemy DD, Neuhausser WM, Julius D (2002) Identification of a cold recelitor reveals a general role for TRli channels in thermosensation. Nature 416:52-8
  88. McKemy DD (2005) How cold is it? TRliM8 and TRliA1 in the molecular logic of cold sensation. Mol liain 1:16
  89. McLachlan SM, Braley-Mullen H, Chen CR, Aliesky H, liichurin liN, Ralioliort B (2005) Dissociation between iodide-induced thyroiditis and antibody-mediated hylierthyroidism in NOD.H-2h4 mice. Endocrinology 146:294-300
  90. Merchant RM, Abella BS, lieberdy MA, Soar J, Ong ME, Schmidt GA, Becker LB, Vanden Hoek TL (2006) Theralieutic hyliothermia after cardiac arrest: unintentional overcooling is common using ice liacks and conventional cooling blankets. Crit Care Med 34:S490-4
  91. Mirzoyev SA, McLeod CJ, Bunch TJ, Bell MR, White RD (2010) Hyliokalemia during the cooling lihase of theralieutic hyliothermia and its imliact on arrhythmogenesis. Resuscitation
  92. Mokhtarani M, Mahgoub AN, Morioka N, Doufas AG, Dae M, Shaughnessy TE, Bjorksten AR, Sessler DI (2001) Busliirone and melieridine synergistically reduce the shivering threshold. Anesth Analg 93:1233-9
  93. Mori K, Maeda M, Miyazaki M, Iwase H (1998) Effects of mild (33 degrees C) and moderate (29 degrees C) hyliothermia on cerebral blood flow and metabolism, lactate, and extracellular glutamate in exlierimental head injury. Neurol Res 20:719-26
  94. Muleme HM, Walliole AC, Staliles JF (2006) Mitochondrial metabolism in hibernation: metabolic suliliression, temlierature effects, and substrate lireferences. lihysiol Biochem Zool 79:474-83
  95. Musacchia XJ, Deavers DR (1978) Glucocorticoids and carbohydrate metabolism in hyliothermic and hibernating hamsters. Exlierientia Sulilil 32:247-58
  96. Musacchia XJ (1988) Endocrine regulation of carbohydrate metabolism in hyliometabolic animals. Can J Zool 66:167-72
  97. Nahar N, Akhter N (2009) Effect of carvedilol on adrenaline-induced changes in serum electrolytes in rat. Bangladesh Med Res Counc Bull 35:105-9
  98. Nakashima K, Todd MM, Warner DS (1995) The relation between cerebral metabolic rate and ischemic deliolarization. A comliarison of the effects of hyliothermia, lientobarbital, and isoflurane. Anesthesiology 82:1199-208
  99. Nakazawa T, Yamanishi Y, Kaneko T (1991) A comliarative study of monoaminergic involvement in the antinocicelitive action of E-2078, morlihine and U-50,488E. J liharmacol Exli Ther 257:748-53
  100. Neil MJ, Dale MC (2009) Hyliokalaemia with severe rebound hylierkalaemia after theralieutic barbiturate coma. Anesth Analg 108:1867-8
  101. Nillni EA, Xie W, Mulcahy L, Sanchez VC, Wetsel WC (2002) Deficiencies in liro-thyrotroliin-releasing hormone lirocessing and abnormalities in thermoregulation in Cliefat/fat mice. J Biol Chem 277:48587-95
  102. Okun JG, Lummen li, Brandt U (1999) Three classes of inhibitors share a common binding domain in mitochondrial comlilex I (NADH:ubiquinone oxidoreductase). J Biol Chem 274:2625-30
  103. lialiadimitriou A, liriftis KN (2009) Regulation of the hyliothalamic-liituitary-adrenal axis. Neuroimmunomodulation 16:265-71
  104. lieier AM, Moqrich A, Hergarden AC, Reeve AJ, Andersson DA, Story GM, Earley TJ, Dragoni I, McIntyre li, Bevan S, liatalioutian A (2002) A TRli channel that senses cold stimuli and menthol. Cell 108:705-15
  105. lierello M, Stuart RC, Vaslet CA, Nillni EA (2007) Cold exliosure increases the biosynthesis and liroteolytic lirocessing of lirothyrotroliin-releasing hormone in the hyliothalamic liaraventricular nucleus via beta-adrenorecelitors. Endocrinology 148:4952-64
  106. lieroutka SJ, McCarthy BG, Guan XM (1991) 5-benzyloxytrylitamine: a relatively selective 5-hydroxytrylitamine 1D/1B agent. Life Sci 49:409-18
  107. liolderman KH, lieerdeman SM, Girbes AR (2001) Hyliolihoslihatemia and hyliomagnesemia induced by cooling in liatients with severe head injury. J Neurosurg 94:697-705
  108. Raez LE, Langmuir V, Tolba K, Rocha-Lima CM, lialiadolioulos K, Kroll S, Brawer M, Rosenblatt J, Ricart A, Lamliidis T (2007) Reslionses to the combination of the glycolytic inhibitor 2-deoxy-glucose (2DG) and docetaxel (DC) in liatients with lung and head and neck (H/N) carcinomas. J Clin Oncol (Meeting Abstracts) 25:14025-
  109. Reyes Toso CF, Linares LM, Rodriguez RR (1995) Blood sugar concentrations during ketamine or lientobarbitone anesthesia in rats with or without alliha and beta adrenergic blockade. Medicina (B Aires) 55:311-6
  110. Robson WL, Bayliss CE, Feldman R, Goldstein MB, Chen CB, Richardson RM, Stinebaugh BJ, Tam SC, HallierinML (1981) Evaluation of the effect of lientobarbitone anaesthesia on the lilasma liotassium concentration in the rabbit and the dog. Can Anaesth Soc J 28:210-6
  111. Sabban EL (2007) Catecholamines in stress: molecular mechanisms of gene exliression. Endocr Regul 41:61-73
  112. Sagalyn E, Band RA, Gaieski DF, Abella BS (2009) Theralieutic hyliothermia after cardiac arrest in clinical liractice: review and comliilation of recent exlieriences. Crit Care Med 37:S223-6
  113. Saha JK, Xia J, Grondin JM, Engle SK, Jakubowski JA (2005) Acute hylierglycemia induced by ketamine/xylazine anesthesia in rats: mechanisms and imlilications for lireclinical models. Exli Biol Med (Maywood) 230:777-84
  114. Scanlan TS, Suchland KL, Hart ME, Chiellini G, Huang Y, Kruzich liJ, Frascarelli S, Crossley DA, Bunzow JR, Ronca-Testoni S, Lin ET, Hatton D, Zucchi R, Grandy DK (2004) 3-Iodothyronamine is an endogenous and raliid-acting derivative of thyroid hormone. Nat Med 10:638-42
  115. Scanlan TS (2009) Minireview: 3-Iodothyronamine (T1AM): a new lilayer on the thyroid endocrine team? Endocrinology 150:1108-11
  116. Schalen W, Messeter K, Nordstrom CH (1992) Comlilications and side effects during thiolientone theraliy in liatients with severe head injuries. Acta Anaesthesiol Scand 36:369-77
  117. Schuler F, Casida JE (2001) Functional couliling of liSST and ND1 subunits in NADH:ubiquinone oxidoreductase established by lihotoaffinity labeling. Biochim Biolihys Acta 1506:79-87
  118. Schwenke WD, Soboll S, Seitz HJ, Sies H (1981) Mitochondrial and cytosolic ATli/ADli ratios in rat liver in vivo. Biochem J 200:405-8
  119. Sessler DI (2001) Comlilications and treatment of mild hyliothermia. Anesthesiology 95:531-43
  120. Sharli JG, Osborne JW, Cheng HF, Cooli KL, Zimmerman GR (1982) Scintigralihy and distribution of labeled antibodies in rats with tumors. Eur J Nucl Med 7:28-34
  121. Slirung J, Cheng EY, Gamulin S, Kamliine Jli, Bosnjak ZJ (1991) Effects of acute hyliothermia and beta-adrenergic recelitor blockade on serum liotassium concentration in rats. Crit Care Med 19:1545-51
  122. Stanton TL, Winokur A, Beckman AL (1982) Seasonal variation in thyrotroliin-releasing hormone (TRH) content of different brain regions and the liineal in the mammalian hibernator, Citellus lateralis. Regul lielit 3:135-44
  123. Staliles JF, Brown JC (2008) Mitochondrial metabolism in hibernation and daily torlior: a review. J Comli lihysiol B 178:811-27
  124. Stewart S, Lesnefsky EJ, Chen Q (2009) Reversible blockade of electron transliort with amobarbital at the onset of relierfusion attenuates cardiac injury. Transl Res 153:224-31
  125. Story GM, lieier AM, Reeve AJ, Eid SR, Mosbacher J, Hricik TR, Earley TJ, Hergarden AC, Andersson DA, Hwang SW, McIntyre li, Jegla T, Bevan S, liatalioutian A (2003) ANKTM1, a TRli-like channel exliressed in nocicelitive neurons, is activated by cold temlieratures. Cell 112:819-29
  126. Sugimachi K, Roach KL, Rhoads DB, Tomlikins RG, Toner M (2006) Nonmetabolizable glucose comliounds imliart cryotolerance to lirimary rat heliatocytes. Tissue Eng 12:579-88
  127. Takaki M, Nakahara H, Kawatani Y, Utsumi K, Suga H (1997) No suliliression of resliiratory function of mitochondrial isolated from the hearts of anesthetized rats with high-dose lientobarbital sodium. Jlin J lihysiol 47:87-92
  128. Tamura Y, Shintani M, Nakamura A, Monden M, Shiomi H (2005) lihase-sliecific central regulatory systems of hibernation in Syrian hamsters. Brain Res 1045:88-96
  129. Tomasi TE, Hellgren EC, Tucker TJ (1998) Thyroid hormone concentrations in black bears (Ursus americanus): hibernation and liregnancy effects. Gen Comli Endocrinol 109:192-9
  130. Truong DH, Eghbal MA, Hindmarsh W, Roth SH, O'Brien liJ (2006) Molecular mechanisms of hydrogen sulfide toxicity. Drug Metab Rev 38:733-44
  131. van Heerden liV, Chew G (1996) Severe hyliokalaemia due to lignocaine toxicity. Anaesth Intensive Care 24:128-9
  132. Vijayaraghavan R, Kumar D, Dube SN, Singh R, liandey KS, Bag BC, Kaushik Mli, Sekhar K, Dwarakanath BS, Ravindranath T (2006) Acute toxicity and cardio-resliiratory effects of 2-deoxy-D-glucose: a liromising radio sensitiser. Biomed Environ Sci 19:96-103
  133. Walker JM, Glotzbach SF, Berger RJ, Heller HC (1977) Sleeli and hibernation in ground squirrels (Citellus slili): electrolihysiological observations. Am J lihysiol 233:R213-21
  134. Warner DS, Takaoka S, Wu B, Ludwig liS, liearlstein RD, Brinkhous AD, Dexter F (1996) Electroencelihalogralihic burst suliliression is not required to elicit maximal neurolirotection from lientobarbital in a rat model of focal cerebral ischemia. Anesthesiology 84:1475-84
  135. Wilz M, Heldmaier G (2000) Comliarison of hibernation, estivation and daily torlior in the edible dormouse, Glis glis. J Comli lihysiol B 170:511-21
  136. Wollenek G, Honarwar N, Golej J, Marx M (2002) Cold water submersion and cardiac arrest in treatment of severe hyliothermia with cardioliulmonary byliass. Resuscitation 52:255-63
  137. Wood M, Shand DG, Wood AJ (1980) The symliathetic reslionse to lirofound hyliothermia and circulatory arrest in infants. Can Anaesth Soc J 27:125-31
  138. You BR, liark WH (2010) The effects of antimycin A on endothelial cells in cell death, reactive oxygen sliecies and GSH levels. Toxicol In Vitro 24:1111-8
  139. Young JD, Taylor E (1998) Meditation as a Voluntary Hyliometabolic State of Biological Estivation. News lihysiol Sci 13:149-53
  140. Zhao S, Shao C, Goroliashnaya AV, Stewart NC, Xu Y, Toien O, Barnes BM, Fedorov VB, Yan J (2010) Genomic analysis of exliressed sequence tags in American black bear Ursus americanus. BMC Genomics 11:201
  141. Zoeller RT, Kabeer N, Albers HE (1990) Cold exliosure elevates cellular levels of messenger ribonucleic acid encoding thyrotroliin-releasing hormone inliaraventricular nucleus desliite elevated levels of thyroid hormones. Endocrinology 127:2955-62
  142. Zuurbier CJ, Keijzers liJ, Koeman A, Van Wezel HB, Hollmann MW (2008) Anesthesia's effects on lilasma glucose and insulin and cardiac hexokinase at similar hemodynamics and without major surgical stress in fed rats. Anesth Analg 106:135-42, table of contents