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

The effect of experimental hypothermia on changes of the electrophysiological equivalent of minute ventilation (Veq) was studied in rabbits under urethane-chloralose general anaesthesia with muscle relaxation and artificial ventilation. The animals were subjected to bilateral vagotomy prior to the experiment. During normothermia (37.5 +/- 0.7 degree C) and hypothermia (29.9 +/- 1.7 degrees C) the animals were given for breathing a hypercapnic mixture of gases (CO2 5% with O2 95%) and asphyxia was produced by switching off the respirator. The arterial blood pressure, blood flow in the common carotid artery, end-expiratory CO2 concentration, "integrated" phernic nerve activity and brain-stem temperature were recorded. The partial pressure of carbon dioxide and oxygen, hydrogen ion concentration and arterial acid-base balance were determined with correction for temperature changes. The equivalent of minute ventilation (being the product of the frequency and amplitude of "integrated" phrenic nerve activity) decreased in hypothermia by 91%, with a simultaneous fall of PaCO2 from 33,48 +/- 3.84 mmHg to 23.40 +/- 3.59 mmHg (by 30%). The hypercapnic stimulus applied during hypothermia produced a fivefold lower Veq value than in normothermia and under control conditions (despite a similar value of PaCO2 of 28.89 +/- 3.12 mmHg). The Veq value approaching that found under normal conditions in normothermia was observed during hypothermia only when asphyxia was induced when the value of PaCO2 was 37.07 +/- 8.74 mm Hg and that of PaO2 was 37.41 +/- 29.11 mmHg. During hypothermia the blood flow in the common carotid artery decreased by 16% when the animals were breathing the hypercapnic mixture. The analysis of the obtained results showed a direct effect of temperature on respiratory activity generation and regulation of arterial blood flow to the brain. It may be supposed also that hypothermia raises the response threshold to CO2 level in the breathed air.
Acta Physiol Pol
PMID:Minute ventilation changes in rabbits during experimental hypothermia. 642 Oct 87

It was tried in this study to determine the effects of temperature and carbon dioxide on the respiratory drive under experimental hypothermia in rabbits under urethane-chloralose anaesthesia after muscle-relaxant administration, after bilateral vagotomy and during artificial ventilation with a biologically-controlled respirator. Hypercapnia was produced in the animals during normothermia (37.3 +/- 0.7 degrees C) and hypothermia (30.0 +/- 1.5 degrees C). The basic physiological parameters and efferent activity of the phrenic nerve were recorded, and arterial blood gasometric parameters were determined. The electrophysiological equivalent of minute ventilation (Veq) decreased during hypothermia by 33% on the average while the PaCO2 value was unchanged. The hypercapnic stimulus applied during hypothermia failed also to raise the Veq value to its initial level. A 9% fall of blood flow was observed in the common carotid artery when the animals received a hypercapnic gas mixture for breathing during hypothermia. The results obtained in this study and earlier observations confirm unequivocally the hypothesis of a direct influence of temperature lowering on respiratory rhythm generation and regulation of arterial blood flow to the brain.
Acta Physiol Pol
PMID:Effect of lowered temperature on respiratory rhythm generation in rabbit. 642 Oct 88

The relative effects of temperature and CO2 on the blood flow in the common carotid artery (CCBF) were investigated in vagotomized, paralyzed rabbits under urethane-chloralose general anaesthesia with artificial ventilation. During hypothermia a 52% fall of CCBF was observed in rabbits ventilated by the classic method. Administration of a hyperkapnic mixture for breathing caused a further 16% CCBF fall, with a simultaneous rise in PaCO2 by 23%. During ventilation with a respirator triggered by phrenic nerve activity hypothermia caused a 30% CCBF fall without changes in PaCO2 value. Administration of the hyperkapnic mixture for breathing caused, in these circumstances, a 9% CCBF fall with a 7% PaCO2 increase. Hyperthermia caused during ventilation by the classic method a 42% rise in CCBF and a 22% PaCO2 rise. The hyperkapnic mixture given for breathing decreased the CCBF by 9% and increased the PaCO2 by 15%. On the other hand, during ventilation with the respirator triggered by phrenic nerve activity no changes were observed in these parameters. This suggests that the thermic stimulus exerts a direct effect on the regulation of the blood flow to the brain, and during hypothermia it prevails over the stimulus produced by CO2.
Acta Physiol Pol
PMID:"Paradoxical" effect of carbon dioxide on common carotid artery blood flow in rabbits during hypothermia and hyperthermia. 644 50

During hypothermia induced by intraperitoneal administration of 2-deoxy-D-glucose (600 mg/kg of body weight) the serum levels of glucose and FFA rise and the hepatic glycogen content falls in relation to rats in control group. The glycogenolytic activity of the serum in vitro determined against liver slices is also higher in the group of rats receiving 2-DG. The obtained results point to an activation of the glycogenolysis process and glycolysis in the organism of rats after administration of hypothermia-inducing doses of 2-DG.
Acta Physiol Pol
PMID:In vitro serum glycogenolytic activity in rats during hypothermia induced with 2-deoxy-D-glucose. 653 17

The antidepressant action of combined treatment with selective inhibitors of noradrenaline (NA) and serotonin (5HT) uptake was investigated using the reserpine and apomorphine hypothermia tests. Desipramine and maprotiline, NA uptake inhibitors, but not fluoxetine and citalopram, selective 5HT uptake inhibitors, antagonized the hypothermias. A combination of NA and 5HT uptake inhibitors antagonized reserpine hypothermia less effectively than the inhibitor of NA uptake alone. The apomorphine hypothermia was antagonized similarly by a NA uptake inhibitor given alone and in combination with a 5HT uptake inhibitor. The results indicate that for antidepressant (antireserpine and antiapomorphine) effect the essential role is played by a noradrenergic mechanism, while the serotonergic mechanism may even produce opposite effect.
Pol J Pharmacol Pharm 1983
PMID:The effect of selective inhibitors of noradrenaline and serotonin uptake on reserpine- and apomorphine induced hypothermia in mice. 660 64

Far-lateral hypothalamus (FLH) and substantia nigra (SN) were destroyed by radio-frequency current (RF lesion) or neurotoxically (6-hydroxydopamine injection) in 4 groups of cats. Hypothermia was observed only after 6-hydroxydopamine injections and RF lesions to FLH. Both methods of SN damage did not affect the body temperature of animals. These results suggest that hypothermia observed in LH syndrome in cats is not directly related to the function of the dopaminergic nigro-striatal system.
Acta Physiol Pol
PMID:The role of dopaminergic nigro-striatal system in the aetiology of the lateral hypothalamic syndrome in cats: is there any deficit in thermoregulation? 666 7

Phenylethylamine (PEA, 50 and 100 microgram ivc) and octopamine (OCT, 50 and 250 microgram ivc) potentiated the tremorine (10 mg/kg ip) induced hypothermia in the rat. This effect was partially antagonized by atropine (10 mg/kg ip). PEA and OCT significantly prolonged the duration of pilocarpine (100 mg/kg iv) induced catalepsy in rats. PEA (100 microgram ivc) and OCT (250 microgram ivc) depressed the acetylcholine (ACh) level in the cerebral cortex and striatum but did not affect it in the hippocampus. In addition, these amines enhanced the synthesis of ACh in the cerebral cortex, and PEA also in the rat striatum.
Pol J Pharmacol Pharm 1981 Oct
PMID:The effect of intraventricular phenylethylamine and octopamine on the central effects of tremorine and pilocarpine and the acetylcholine level in the rat brain. 679 57

Pirenzepine, (5,11-dihydro-11-[(4-methylpiperazin-1-yl)-acetyl]-6H-pyrido-[2,3] [1,4]-benzodiazepin-6-one dihydrochloride), tested on rats and mice, did not demonstrate any conspicuous behavioral action: it did not counteract reserpine hypothermia in mice, the L-DOPA hypermotility of mice, and (with the exception of very large doses) the amphetamine hypermotility in mice and rats. The drug neither prolonged the time of immobility of rats in the behavioral despair test, nor affected the central serotonin system in rats in tests for 5-hydroxytryptophan-induced head twitches, tryptamine-induced convulsions and fenfluramine-induced hyperthermia at high ambient temperature. Pirenzepine did not affect either the hind limb flexor reflex in the spinal rat, nor the action of serotoninomimetics of it. The investigated compound had strong peripheral cholinolytic action as it inhibited salivation and lacrimation in the oxotremorine test. The oxotremorine tremor was weakened only by very high doses of pirenzepine. LD50 of the drug in mice was 412 mg/kg ip.
Pol J Pharmacol Pharm 1981
PMID:Central action of pirenzepine. 689 18

Intraventricular injection of prostacyclin (PGI2) slightly depressed the general behavior and produced a weak hypothermia in rats. It shortened the response to a thermal nociceptive stimulus and intensified catalepsy caused by chloropromazine and haloperidol. PGI2 did not change concentration of noradrenaline, 4-hydroxytryptamine, 5-hydroxyindoleacetic acid and dopamine in different brain areas. It markedly lowered blood pressure and increased respiration. The duration of central hypotensive effect of PGI2 was shortened after 6-hydroxydopamine on 5,6-dihydroxytryptamine pretreatment. The possible involvement of a central mechanism in the hypotensive action of PGI2 requires further clarification.
Pol J Pharmacol Pharm 1981 Nov
PMID:Studies on the behavioral and hypotensive effects of intraventricular prostacyclin (PGI2) in rats. 703 17

During short-lasting hypothermia in rats the activity of isocitrate dehydrogenase (E.C.1.1.1.42) and malic dehydrogenase (E.C.1.1.1.37) was determined in the mitochondrial fraction of liver cells, myocardial cells and skeletal muscle fibres of the femoral muscle and no statistically significant differences were found between the obtained values and those in a control group. On the other hand, the activity of glucose-6-phosphate dehydrogenase (E.C.1.1.1.49) in the cytoplasmic fraction of these tissues was decreased in the hypothermic rats by 46% in the liver, by 50% in the myocardium and by 59% in the skeletal muscle of the thigh. A possible cause of this reduced activity of this enzyme in hypothermia could be changes in the structure of the enzymatic protein, deficiency of the hormone activating the enzyme, that is insulin, and/or inhibition of the pentose-phosphate cycle by fatty acids released in excess.
Acta Physiol Pol
PMID:Activity of certain enzymes in the mitochondrial and cytoplasmic fractions of liver cells, myocardium and skeletal muscle of the rat during short-lasting hypothermia. 718 57


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