Organization of central hyperthermic mechanisms in helium-cold hypothermic hamsters.
We have investigated the ability of three hyperthermic stimuli (PGE2, 5-HT and ACh) to elicit hyperthermia in the Helium-Cold (He-Cold) hypothermic hamster. Hamsters in these conditions are poikilothermic and will passively follow room temperature in a regulated cold room. Animals were injected centrally at AH/POA sites via an indwelling guide tube at body temperatures maintained between 9-12 degrees C. Active sites in the AH/POA were determined prior to the experiment by PGE2 injection. PGE2 injection at an effective AH/POA site immediately reversed the anesthetic induced hypothermia in warm air. Hamsters were induced into hypothermia by the He-Cold induction method and body temperatures were maintained in a 9 degrees C cold room. Colonic temperatures were monitored at 5 minute intervals by a YSI thermistor probe and telethermometer. Central injections of 5-HT (2 micrograms/microliter) and ACh (50 micrograms/microliter) at effective AH/POA sites evoked significant increases in colonic temperature in He-Cold hamsters. PGE2 injections were not different from saline control injections and did not elicit pronounced temperature changes in these animals. Specific blockade of the 5-HT and ACh temperature increases was demonstrated with specific antagonist injections. The results suggest that the central organization of heat-gain mechanisms in the AH/POA is the same as normothermic animals even at temperatures well below those previously investigated.
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D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001696:Biomechanical Phenomena; D001831:Body Temperature / Q000187:drug effects; D003080:Cold Temperature; D006224:Cricetinae; D015232:Dinoprostone; D005260:Female; D005334:Fever / Q000139:chemically induced / Q000209:etiology / Q000503:physiopathology*; D006371:Helium; D007031:Hypothalamus / Q000503:physiopathology*; D007267:Injections; D007649:Ketamine / Q000494:pharmacology; D008297:Male; D008647:Mesocricetus; D011458:Prostaglandins E / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology
D011458:Prostaglandins E; D012702:Serotonin Antagonists; D006371:Helium; D012701:Serotonin; D007649:Ketamine; D001285:Atropine; D015232:Dinoprostone; D000109:Acetylcholine