Hypothermia induced by centrally administered vasopressin in rats. A structure-activity study.

Vasopressin and related peptides cause short-lasting hypothermia when injected into the lateral ventricle of the rat. In the present study, the structure-activity relationships for the induction of this effect were examined. For the agonist peptides studies, the structural requirements were found to be similar to those required to cause peripheral vasoconstriction ant to induce behavioral excitation in mice. However, an antagonist of the pressor and behavioral effects of vasopressin was ineffective in antagonizing the hypothermic response. Moreover, this analog and another pressor antagonist themselves caused hypothermia. Comparison with the structure-activity relationships for other effects on the central nervous system strongly suggests that the hypothermic response is unrelated to the effects of vasopressin on consolidation of memory, development of tolerance to drugs, and mechanisms of reinforcement.