Intracerebroventricular and septal injections of arginine vasopressin are not antipyretic in the rabbit

Arginine vasopressin (AVP) has been reported to have an antipyretic effect in the ewe and guinea pig near term. Perfusions with AVP of sites in the septal region also reduced fever in non-pregnant sheep. In the present experiments adult rabbits with third cerebral ventricular or septal cannulas were restrained in a 23°C environment, and rectal temperature was recorded every 10 min. Fever induced by IV administration of leukocytic pyrogen was not reduced by AVP (25–100 ng) given intraventricularly 20 min later. Doses of 1–5 μg AVP injected into the septum likewise were not antipyretic but actually caused an increase in fever. This augmentation of the febrile response is consistent with results of previous studies in this laboratory in which AVP increased hyperthermia in a hot environment and enhanced hyperthermic responses to PGE₂. The data from these experiments provide no evidence that central AVP is an endogenous antipyretic in rabbits; rather, it may be that central AVP augments fever in this species.