Ethanol-induced hypothermia in rats: possible involvement of opiate kappa receptors.
The effect of the opiate antagonists naloxone and MR2266 on ethanol-induced hypothermia and changes in Ca2+-stimulated Mg2+-ATPase activity in brain regions were investigated in the present study. Administration of different doses of ethanol (0.5-2 g/kg, IP) produced a dose-dependent hypothermia. Ca2+/Mg2+-ATPase activity in the hypothalamus was stimulated at 30 min and 2 hr after ethanol (2 g/kg, IP) treatment. In cortex, enzyme activity was inhibited by ethanol at 30 min with no change seen at 2 hr. Naloxone (7.5 mg/kg, SC) at a dose which did not affect body temperature or enzyme activity, partially inhibited ethanol-induced hypothermia and enzyme activity at the earliest time (30 min) but not at 2 hours. The opiate Kappa antagonist MR2266 (5 mg/kg, SC), however, significantly protected against ethanol hypothermia and enzyme activation measured at 30-120 min. This evidence suggests that ethanol-induced hypothermia and subsequent activation changes of Ca2+/Mg2+-ATPase in the hypothalamus may be regulated by opiate Kappa receptors, and that Ca2+ ions play an important role in mediating the effects of ethanol.
D000818:Animals; D001575:Benzomorphans / Q000008:administration & dosage; D001831:Body Temperature / Q000187:drug effects*; D001921:Brain / Q000201:enzymology; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004347:Drug Interactions; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009270:Naloxone / Q000008:administration & dosage; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects*; D017473:Receptors, Opioid, kappa
D001575:Benzomorphans; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D009270:Naloxone; D000431:Ethanol; C027247:MR 2266; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases