A CENTRAL HYPOTHERMIC RESPONSE TO PILOCARPINE IN THE MOUSE

¹ Department of Pharmacology, Albert Einstein College of Medicine, New York, New York

Cholinoceptive neurons appear to participate in central nervous system control of body temperature in the mouse. Systemic administration of pilocarpine, physostigmine, tremorine and oxotremorine preduced a profound fall in rectal temperature which was antagonized by i.p. scopolamine but not by the quaternary blocking agent, methscopolamine. In mice that were first treated with methscopolamine, i.p. pilocarpine produced a dramatic hypothermic response that was dose-dependent between 1 and 100 mg/kg. This response was influenced by the ambient temperature and possibly, in some complex way, by body temperature. A highly significant linear correlation was discovered between the hypothermic response and the initial (preinjection) temperature; this relationship was probably the result of an emotional response to the measurement procedure itself and not due to an effect of pilocarpine. These findings are consistent with the hypothesis that acetylcholine is the transmitter liberated from or acting upon interneurons in the hypothalamic thermoregulatory zone which inhibit the production and conservation of body heat in the mouse.