Vasopressin and conditioned flavor aversion in aged rats.

The effect of lysine vasopressin on the performance of young-adult and old rats subjected to a conditioned flavor aversion procedure was studied. Young rats maintained an aversion to a 0.1% saccharin solution significantly longer than did older rats. Treatment with lysine vasopressin ( 1 microgram/kg) during the recovery period prolonged the aversion in both age groups. A single injection of lysine vasopressin prior to the aversion procedure significantly reduced the age difference in extinction. These observations support the hypothesis that age-dependent changes in endogenous vasopressin synthesis or secretion underlie some of the behavioral deficits observed in old animals.