Vasoactive intestinal peptide (VIP) causes memory impairment in passive avoidance responding of the rat.

Our previous studies demonstrated that CCK-8 and its analog, cerulein (CER), have a potent preventive action on experimental amnesia, and that VIP has reciprocal action against CCK-8 and CER. Since VIP has been reported to cause amnesia, we carried out the present experiments to confirm this action and to examine the preventive effect of CER on VIP-induced amnesia. In the passive avoidance response, central administration, but not peripheral injection, of VIP caused amnesia; the effective portion of the molecule was found to be located in the N-terminus amino acid sequence. Secretin and PACAP, which have similar molecular structures to that of VIP, had no amnestic action. Preadministration of CER prevented VIP-induced memory deficit. The VIP antagonists did not affect amnesia induced by electroconvulsive shock and scopolamine. It was concluded that CER prevents VIP-induced memory deficit in the passive avoidance response of the rat.