Effects of intracerebral micro-injection of sodium salicylate on temperature regulation in the rabbit.

1. Symmetrical, bilateral micro-injections (10 mul.) of 6-30 mug sodium salicylate have been made into various parts of the brains of febrile and afebrile rabbits.2. In rabbits with fever induced by an intravenous infusion of endogenous pyrogen, micro-injections of sodium salicylate produced antipyresis when given into the preoptic hypothalamus and the mid-brain.3. In afebrile rabbits, micro-injections of sodium salicylate into these areas were without effect on temperature.4. The results suggest that at least part of the antipyretic effect of salicylates may be mediated by antagonizing the effects of endogenous pyrogen within these areas of the brain.