title: Biphasic changes in body temperature produced by intracerebroventricular injections of histamine in the cat.
abstract: 1. Intracerebroventricular administration of histamine to cats caused hypothermia followed by a rise in body temperature. 2-Methylhistamine caused a similar biphasic response, while 3-methylhistamine had no effect on body temperature and 4-methylhistamine produced a delayed hyperthermia. Some tolerance to the hypothermic activity developed when a series of closely spaced injections of histamine was given. 2. Doses of histamine and 2-methylhistamine which altered body temperature when given centrally were ineffective when infused or injected I.V. 3. Pyrilamine, an H1-receptor antagonist, prevented the hypothermic response to histamine. 4. Hypothermic responses to histamine at an environmental temperature of 22 degrees C were comparable to responses in a cold room at 4 degrees C in both resting animals and animals acting to depress a lever to escape an external heat load. A change in error signal from the thermostat could account for these results. However, lesser degrees of hypothermia developed when histamine was given to animals in a hot environment. In some, but not all animals, this smaller response could be attributed to inadequate heat loss in spite of maximal activation of heat-loss mechanisms. 5. The hyperthermic response to histamine was antagonized by central, but not peripheral, injection of metiamide, an H2-receptor antagonist. 6. The results indicate that histamine and related agents can act centrally to cause both hypothermia, mediated by H1-receptors, and hyperthermia, mediated by H2-receptors.
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D001921:Brain / Q000502:physiology*; D002415:Cats; D004305:Dose-Response Relationship, Drug; D006632:Histamine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology*; D007276:Injections, Intraventricular; D008785:Metiamide / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors
chemical_list: D008785:Metiamide; D006632:Histamine; D011738:Pyrilamine