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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Electrophysiological aspects of thiamine depletion in the rat induced by dietary deficiency are described. Behavioral changes as well as qualitative and quantitative alterations in the sensitivity of cerebellar Purkinje cells to iontophoretically-applied 5-hydroxytryptamine (5-HT) were observed. Thiamine-deficient rats were characterized essentially by ataxia, piloerection, paresis, apparent weakness, and hypothermia after 4-6 weeks on a thiamine-free diet. Basal Purkinje cell firing frequency was unaffected by thiamine deficiency. The response of Purkinje cells to iontophoretically-applied 5-HT was solely inhibitory in deficient rats. In control rats, however, responses to 5-HT were excitatory, biphasic, or inhibitory. Neurons in the thiamine-deficient animals were more sensitive to the inhibitory effects of 5-HT, as demonstrated by a significant parallel shift to the left of the dose-response curve. Durations of 5-HT effects were similar in both groups. Dose-response relationships for GABA-induced inhibition of Purkinje cell firing from thiamine deficient and control rats did not differ from one another. These data demonstrate a relatively selective effect of thiamine depletion on cerebellar serotonergic neurotransmission assessed electrophysiologically. We believe there is up-regulation of 5-HT receptors on Purkinje cells caused by thiamine deficiency-induced impairment of indoleamine input to the cerebellum from raphe and related nuclei.
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PMID:Enhanced sensitivity of cerebellar Purkinje cells to iontophoretically-applied serotonin in thiamine deficiency. 398 3

Cranio-cerebral hypothermia (temperature of the body 32-30 degrees C, of the brain 29-27 degrees C) was studied for its effect on the reuptake of neuromediators (3H-noradrenaline and [14C]GABA) by the cortex and hypothalamus synaptosomes of the rat brain. It was found that the reuptake of [3H]noradrenaline by the cortex synaptosomes under narcosis and cranio-cerebral hypothermia was inhibited much stronger than that by the hypothalamus synaptosomes. At the same time GABA-ergic synapses of the cortex and hypothalamus were not sensitive to narcosis. Cranio-cerebral hypothermia essentially inhibited the reuptake of [14C] GABA by synaptosomes and hypothalamus.
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PMID:[Effect of hypothermia on reuptake of neuromediators by synaptosomes]. 400 72

In acute ethanol studies aminooxyacetic acid (AOAA) alone produced marked hypothermia although a test dose of ethanol was able to produce a further drop in body temperature in AOAA treated mice. Even though tolerance to ethanol-induced hypothermia was present in ethanol-dependent mice, AOAA administration was able to produce a further decrease in body temperature. Bicuculline potentiated ethanol-induced hypothermia in the acute studies but the tolerance to hypothermia which had developed in ethanol-dependent mice prevented the bicuculline-induced potentiation of ethanol hypothermia. AOAA markedly potentiated acute ethanol-induced motor incoordination whereas bicuculline had no effect. Although partial tolerance had developed to ethanol-induced motor incoordination in dependent mice, AOAA potentiated, whereas a lower dose of bicuculline antagonized, motor incoordination. In the acute studies ethanol had a biphasic effect on AOAA-induced GABA accumulation in the hypothalamus and corpus striatum: low doses prevented and a slightly higher dose was without effect on GABA accumulation. Ethanol-dependent mice were unable to respond to an AOAA-induced increase in GABA accumulation although basal levels of GABA were unaffected by chronic ethanol ingestion. The results show that brain GABA or GABA-mediated central mechanisms may be involved in the mediation of ethanol-induced motor incoordination but not hypothermia.
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PMID:GABA mediation of the central effects of acute and chronic ethanol in mice. 403 3

1 The cerebral ventricles of dogs under intravenous pentobarbitone sodium anaesthesia, were perfused with artificial cerebro-spinal fluid (CSF) at a rate of 0.4-0.5 ml/min from the ventricular to the aqueductal cannulae. The effluent was collected from the aqueductal cannula in 20 min samples. The animals' temperatures were recorded from the rectum.2 gamma-Aminobutyric acid (GABA) 0.1-5 mg when injected into the ventricles produced variable temperature effects. Doses of 0.1 and 0.5 mg always produced hyperthermia and 1 and 5 mg doses sometimes produced hyperthermia and sometimes hypothermia.3 Intraventricular perfusion with 2-bromolysergic acid diethylamide (BOL) and hyoscine did not block hyperthermia. Tests on the rat isolated stomach strip or the guinea-pig isolated superfused ileum for the possible release, respectively, of 5-hydroxytryptamine or acetylcholine by GABA were negative.4 When tested for the presence of prostaglandin E(PGE)-like substances on the isolated rat stomach strip, both the control effluent and the GABA effluent showed activity, the latter being much more potent. There was a temporal correlation between this effect and hyperthermia. Intraventricularly administered sodium salicylate converted the GABA-induced hyperthermia to hypothermia and blocked the release of PGE-like substances.5 Hypothermia induced by GABA alone or in the presence of sodium salicylate was associated with the release of noradrenaline into the effluent.6 Intraventricular administration of GABA in reserpinized dogs produced hyperthermia and not hypothermia. Similar results were obtained with phentolamine perfusion in normal dogs.7 Perfusion with calcium-free solution blocked both the noradrenaline-releasing and hypothermic actions of GABA.8 It is concluded that hyperthermia associated with intraventricular injections of GABA is due to the release of PGE-like substance and hypothermia is due to the release of noradrenaline.
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PMID:Analysis of the effects on body temperature of intracerebroventricular injection in anaesthetized dogs of gamma-aminobutyric acid. 415 52

Administration of thyroliberin (TRH) to reserpinized mice causes tremor and counteracts the hypothermia in a dose-dependent fashion. The thyroliberin response is inhibited by gamma-hydroxybutyric acid (GHB) and baclofen, but not by other, more specific GABA-ergic agents, such as THIP, gamma-acetylenic GABA, and sodium valproate. Picrotoxin neither potentiates nor inhibits the thyroliberin actions. Nor are the thyroliberin effects dependent on cholinergic, monoaminergic or histaminergic mechanisms. The results repudiate a current hypothesis, that the peptide actions may be mediated by GABA-ergic pathways in the brain.
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PMID:Thermic and tremorogenic effects of thyroliberin (TRH) in reserpine-treated mice--the non-involvement of GABA-ergic mechanisms. 611 36

1. Hypothermia in midwinter revealed a marked increase in GABA and glutamine due to active decarboxylation and amidation of glutamic acid. This influenced the glutamate-aspartate pathway and resulted in a significant drop in levels of both acids. 2. Elevated levels of GABA and taurine during hibernation pointed to their role as inhibitory neurotransmitters. 3. Amidation of glutamate induced a noticeable drop in ammonia concurring with increased urea and low uric acid levels. 4. Hypothermia in summer revealed a significant role of temperature as a determining factor in the hibernation cycle. Arousal was a repeated, though reversed, phenomenon in this cycle.
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PMID:Hibernation hypothermia and metabolism in hedgehogs--changes in free amino acids and related compounds. 612 98

Pipecolic acid (PA) is an intermediate of lysine metabolism in the mammalian brain. Recent findings suggest a functional connection of PA as neuromodulator in GABAergic transmission. Since many drugs are postulated to produce their effects by interaction with the central GABA system, the influence of PA on the anticonvulsant activity of phenobarbital was examined. Pretreatment of mice with 50 mg . kg-1 of PA potentiated the suppressing effects of the barbiturate on electrically and chemically induced convulsions. However, there was no potentiation of the behavioral effects and hypothermia induced by phenobarbital. PA itself had no or only little effect on the convulsions, motor function and rectal temperature when given in i.p. doses up to 500 mg . kg-1. Intraventricular administration of 500 microgram of PA also did not suppress either type of convulsion, although it produced ptosis, hypotonia, sedation and hypothermia. The results are discussed in relation to GABA system.
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PMID:Potentiation of phenobarbital-induced anticonvulsant activity by pipecolic acid. 628 9

Rats subjected to non-noxious, anxiogenic stressors were found to exhibit either hyperthermia or hypothermia depending on the nature of the stressor. The present work examines the effects of naloxone (Nx), diazepam (DZP) and gamma-acetylenic GABA (AcG), an inhibitor of GABA catabolism, on these phenomena. Nx reduced stress hyperthermia and basal temperature by similar amounts; it did not affect stress hypothermia. DZP also reduced basal Tb but was able to completely inhibit and even reverse stress hyperthermia and to reduce stress hypothermia. The effects of AcG were similar to those of DZP. In conclusion, it appears that endogenous opioids are not involved in the thermic responses to our emotional stressors whereas GABA would be an important modulator. It is suggested that DZP, through a GABAergic link might inhibit the release of hyperthermic pituitary factors from the neurointermediate lobe and of hypothermic substances from the anterior lobe.
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PMID:Hyper- and hypothermia induced by non-noxious stress: effects of naloxone, diazepam and gamma-acetylenic GABA. 668 38

The effects of elevated levels of GABA, glycine, or taurine on the rate of protein synthesis in plasma, brain, liver, and muscle of adult mice were measured in in vivo experiments after a flooding dose of labeled valine. Elevation of these amino acids caused hypothermia; keeping the animals in an incubator maintained physiological body temperature. The increase in GABA or glycine did not affect the rate of protein synthesis in these tissues to a significant degree. The increase in taurine levels caused inhibition of valine incorporation in plasma, liver, and muscle, while brain protein synthesis was unaffected. When glycine was increased in brain, the uptake of labeled free valine in the brain was greater.
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PMID:Brain protein synthesis rates are not sensitive to elevated GABA, taurine, or glycine. 673 88

Trimethyltin (TMT) induced a dose-dependent antinociceptive and hypothermic effect in mice. Antinociception was not attenuated by naloxone but was reversed by atropine. TMT, however, was ineffective in displacing (3H)-QNB binding in vitro and did not affect (3H)-QNB binding or acetylcholinesterase activity after in vivo administration. The ethyl ester of nipecotic acid, a specific inhibitor of synaptosomal GABA uptake, exerted a similar antinociceptive effect that could be blocked by atropine. The GABA receptor antagonist bicuculline attenuated antinociception induced by TMT and nipecotic acid ethyl ester but not by morphine or oxotremorine. Gamma-Vinyl GABA, an irreversible inhibitor of GABA metabolism, prolonged TMT but not morphine-induced antinociception. In contrast, neither the dose-response nor the time course of TMT-induced hypothermia were affected by any of the drugs tested. The findings suggest that the GABAergic system may be involved in TMT induced antinociception; however, the mechanism responsible for the hypothermic effect of TMT is not apparent.
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PMID:Antinociceptive and hypothermic effects of trimethyltin. 689 Jun 11


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