Vasopressin accelerates appetitive discrimination learning and impairs its reversal

Rats were trained in a semi-automated Y maze to find food at the end of the lighted arm. Those treated with 10 μ g lysine vasopressin, 90 min before training learned the response to a 9 10 correct choice criterion significantly faster than saline treated animals. There was no difference in rate of forgetting between the treatment groups, as evidenced by a retention test, 3 weeks after training. There was no direct effect of vasopressin on retrieval, since animals treated before the retention test performed at the same level as non treated animals. Finally, vasopressin impaired reversal from light to dark. In a second experiment, the acquisition facilitation seen in Exp. I was replicated, but there was no effect of the treatment on animals trained to dark SD. However, the impairment seen in Exp. I when vasopressin treated animals, trained to light, were reversed to dark, was replicated in this experiment in animals trained to dark and reversed to light. Previous demonstrations of vasopressin facilitation of learning and memory have, with few exceptions, relied on shock avoidance tasks. The present experiments demonstrate a reliable facilitation of appetitive learning by vasopressin. The fact that vasopressin impairs reversal may be due to an increased tendency to perseverate.