Differential effects on temperature of chlorpromazine injected into PO/AH and medulla oblongata of the rat.

Hyperthermic responses developed after injections of chlorpromazine into the preoptic/anterior hypothalamic (PO/AH) region of unrestrained rats. Sites near hte posterior border of the anterior hypothalamus were the most sensitive. Injections of chlorpromazine into the medulla oblongata did not alter rectal temperature in intact rats but caused hypothermic responses when the PO/AH region had been destroyed. These results provide additional evidence for a secondary temperature control in the medulla which ordinarily responds minimally to drugs and which may be suppressed by an intact primary control in the PO/AH region.