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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 nicotine on the neuroleptic-induced changes in striatal dopamine (DA) metabolism of mice was studied. To investigate the mechanism of action of nicotine, its interactions with apomorphine (APO) and gamma-hydroxybutyric acid (GHBA) were also investigated. Mice were given nicotine, (0.3-3 mg/kg subcutaneously) repeatedly (4 times) at 30 min. intervals. Haloperidol (HAL), (+/-)-sulpiride (SUL), APO or GHBA were administered after the second nicotine dose. Hexamethonium was given to prevent the effects of nicotine on autonomic ganglia. The striatal contents of DA and of its metabolites homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-methoxytyramine (3-MT) were measured. The drug-induced hypothermia in mice was controlled by increasing ambient temperature. At ambient temperature of 32-34 degrees nicotine and HAL increased the striatal DOPAC and HVA contents additively, whereas APO counteracted the effects of nicotine at this ambient temperature. At 20-22 degrees nicotine decreased the 3-MT content which indicates reduced release of DA. In hypothermic mice nicotine inhibited better the HAL- and SUL-induced increases of HVA content than those of DOPAC content suggesting that the neuroleptic-induced increases in DOPAC and HVA contents are mediated partly by different mechanisms. In APO-treated mice both the GHBA- and nicotine-induced decreases of 3-MT content fell further. GHBA did not alter the nicotine-induced decrease of 3-MT content and so this effect of nicotine may be mediated indirectly via GABAergic neurones. Unlike GHBA and APO nicotine decreased 3-MT content only in hypothermic mice.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Dual effects of nicotine on neuroleptic-induced changes of striatal dopamine metabolism in mice. 256 30

gamma-Aminobutyric acid (GABA) intraperitoneally injected (i.p.) produced a dose-dependent hypothermia in restrained rats. GABA-induced hypothermia (1000 mg kg-1) was antagonized by pretreatment with atropine (2.5 and 10 mg kg-1 i.p.), hyoscine butylbromide (2.5 mg kg-1 i.p.), hexamethonium (0.75 mg kg-1 i.p.) or physostigmine (0.2 mg kg-1 s.c.). Hexamethonium (7.5 mg kg-1 i.p.) did not influence the hypothermia induced by GABA. The antagonism by physostigmine of GABA-induced hypothermia was attenuated by pretreatment of the rats with either alpha-methyl-p-tyrosine (200 mg kg-1 i.p.) or hexamethonium (7.5 mg kg-1 i.p.), but it was potentiated by either atropine (5 mg kg-1 i.p.) or hexamethonium (0.75 mg kg-1 i.p.). The data indicate that GABA-induced hypothermia may be partly mediated by acetylcholine release. Muscarinic receptors may play an important role in the effect of GABA. The results support the hypothesis of nicotinic presynaptic receptors modulating noradrenergic nerve endings that play a part in the hypothermic response of GABA.
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PMID:Hypothermic effect of GABA in conscious stressed rats: its modification by cholinergic agonists and antagonists. 289 Jul 37

The ability of nicotinic receptor blockers, mecamylamine and pempidine, to antagonize the changes in striatal dopamine (DA) metabolism induced by repeated nicotine administration was studied. The contents of DA and its metabolites 3-methoxytyramine (3-MT), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured. Mice kept at 20-22 degrees C were given nicotine, 3 mg/kg, s.c., four times, at 30 min intervals, and sacrificed 20 min after the last dose. Hexamethonium, 10 mg/kg, i.p., was administered at 30 min before the first nicotine dose in order to prevent the peripheral effects of nicotine. Mecamylamine, 0.6 or 10 mg/kg, i.p., and pempidine, 0.6 or 20 mg/kg, i.p., were given at 60 min before sacrifice. Mecamylamine and pempidine decreased clearly the striatal 3-MT content, which suggests that the nigrostriatal dopaminergic neurons are physiologically controlled by a stimulatory nicotinic mechanism. The repeatedly administered nicotine caused deep hypothermia, and increased the striatal DOPAC content but decreased the 3-MT and HVA contents. The small dose of mecamylamine, which was the only dose found to effectively antagonize the nicotine-induced hypothermia, antagonized the decrease of HVA content. The large but not the small doses of mecamylamine and pempidine antagonized the nicotine-induced increase of DOPAC content but none of the doses studied antagonized the decrease of 3-MT content. Thus it seems that nicotine decreases the 3-MT content by a mechanism distinct from the mechanism mediating the increase of the DOPAC content. The decreased 3-MT content most probably results from desensitization of nicotinic cholinergic receptors (nAChR) and following decrease of cholinergic regulation of nigrostriatal dopaminergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Antagonism of the nicotine-induced changes of the striatal dopamine metabolism in mice by mecamylamine and pempidine. 318 44

Further information about the nicotine-induced changes in striatal dopamine metabolism in hypothermic mice was searched by measuring the contents of dopamine and its metabolites (3,4-dihydroxyphenylacetic acid, DOPAC; 3-methoxytyramine, 3-MT; and homovanillic acid, HVA) after blocking the synthesis of dopamine by alpha-methyl-p-tyrosine (alpha-MT). This method gave a possibility to study the effect of nicotine on the metabolism of dopamine in two pools (the cytoplasmic "newly-synthesized" dopamine and the granular dopamine). 3 mg/kg of (-)nicotine was given s.c. four times, at 110, 80, 50 and 20 min, and alpha-MT (250 mg/kg i.p.) at 60 min before sacrifice. To prevent the peripheral effects of nicotine all mice were given hexamethonium (10 mg/kg i.p.) at 140 min before sacrifice. Hexamethonium did not alter striatal dopamine metabolism. Experiments were performed at 20-22 degrees C at which temperature nicotine induced hypothermia or at 32-34 degrees C. The alpha-MT-induced proportional decrease of 3-MT content was clearly less than that of dopamine content. On the contrary the alpha-MT treatment decreased the DOPAC content proportionally more than the dopamine content. Thus DOPAC could not be solely formed from the same dopamine pool as 3-MT. These results indicate that 3-MT reflects best the metabolism of the granular dopamine and DOPAC that of the "newly-synthesized" dopamine. In hypothermic mice nicotine administration reduced the alpha-MT-induced depletion of the dopamine content.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Different changes in striatal dopamine metabolism induced by nicotine in mice kept at different ambient temperatures. Evidence for partly separate metabolic routes of dopamine derived from separate compartmentations. 382 29

In the present study, cross-tolerance between hypothermia induced by morphine and nicotine in mice has been investigated. Different doses of morphine or nicotine induced dose-dependent hypothermia. The sub-maximal doses of both drugs were used for interaction studies. Administration of mecamylamine either intracerebroventricularly (2-6 microg/animal icv) or intraperitoneally (0.5 and 1 mg/kg ip) decreased both morphine- or nicotine-induced hypothermia. Naloxone either intracerebroventricularly (2-6 microg/animal) or intraperitoneally (1 and 2 mg/kg) reduced the response to morphine, but not nicotine's response. Hexamethonium (5 and 10 mg/kg ip) caused a slight decrease in morphine's hypothermia, but not that of nicotine. Nicotine's response was decreased in the animals which were made tolerant to hypothermic effect of morphine. Pre-treatment of the animals with low doses of morphine (12.5 or 25 mg/kg), once daily for 3 days, did not cause significant tolerance to the hypothermic response to morphine or nicotine. However, the administration of low doses of morphine (12.5 or 25 mg/kg) plus nicotine (2 mg/kg), once daily for 3 days, increased levels of tolerance to hypothermia induced by either drug. It is concluded that nicotinic receptor mechanism may play a role in morphine-induced hypothermia and there is cross-tolerance between the two drugs.
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PMID:The possible cross-tolerance between morphine- and nicotine-induced hypothermia in mice. 1126 33