Central infusion of vasopressin in male rats accelerates extinction of conditioned taste avoidance induced by LiCl

In shock avoidance tasks, extinction is prolonged when vasopressin is infused into the lateral ventricle after an acquisition session. Experiments were performed to determine whether a dose of vasopressin that does not induce conditioned taste avoidance (CTA) could prolong extinction of a LiCl-induced CTA when it is infused into the lateral ventricle of Sprague-Dawley male rats after acquisition. The first experiment was designed to determine whether infusion of vasopressin into the lateral ventricle would induce a CTA. Consumption of a sucrose solution was paired with infusion of vasopressin or saline, and even after two pairings, none of the vasopressin-treated rats showed decreases in sucrose consumption. Therefore, in the second experiment, this same dose of vasopressin was infused into the lateral ventricle 50 min after consumption of a sucrose solution was paired with an injection of LICI. Vasopressin increased the rate of extinction of the LiCl-induced CTA. These results are the opposite of what has been found after peripheral administration of vasopressin before acquisition and/or extinction of a LiCl-induced CTA. Possible reasons for the difference in the direction of the effect on extinction include differential effects of vasopressin depending on the route of administration, the timing of injection, and the presence of aversive effects produced by the neuropeptide. (C) 2002 Elsevier Science Inc.