Influence of chronic intracerebroventricular infusion of vasoactive intestinal peptide (VIP) on memory processes in Morris water pool test in the rat.

In our previous study, bolus injection of VIP into the lateral cerebral ventricle, at nonphysiological high doses, has been shown to produce amnesia. Accordingly, in the present study, VIP was infused chronically into the cerebral ventricle of the rat at a rate of 10 ng per day for 2 weeks. During the infusion period, the animals were subjected to the Morris water pool test. The VIP infusion caused an apparent impairment of memory, particularly in the acquisition of new information; VIP(1-12) also caused similar impairment, but to a lesser extent. The VIP antagonists did not affect the performance of learned tasks. However, cerulein treatment prevented the VIP-induced memory impairment.