The effect of intraseptally applied vasopressin on thermoregulation in the rat

The thermoregulatory effects of intraseptal injection of arginine vasopressin were studied in eight rats in which a thermode and a bilateral cannula had been chronically implanted into the preoptic area and lateral septa, respectively. Intraseptal injection of vasopressin completely suppressed the increase in heat production and body temperature elicited by cooling the preoptic area, but did not appear to affect vasomotor tone. Vasopressin also inhibited heat production in a cold environment, and thus induced a marked drop in core temperature; skin temperature did not, however, fall as much as core temperature suggesting that some vasodilatation occurred. At an ambient temperature in the upper range of thermoneutrality vasopressin had no effect on the thermoregulatory variables studied. It is concluded that vasopressin does not reduce the normal set point temperature and that its main effect is to inhibit thermoregulatory heat production. This effect may explain its antipyretic action.