SYSTEMIC ADMINISTRATION OF ACTH OR VASOPRESSIN REVERSES THE AMNESTIC EFFECT OF POSTTRAINING BETA-ENDORPHIN OR ELECTROCONVULSIVE SHOCK BUT NOT THAT OF INTRAHIPPOCAMPAL INFUSION OF PROTEIN-KINASE INHIBITORS

Retrograde amnesia was induced in rats trained in step-down inhibitory avoidance by four different treatments: an ip injection of beta-endor phin (1.0 mu g kg), an electroconvulsive shock (ECS), an intrahippocam pal infusion of the calcium/calmodulin protein kinase II inhibitor, KN 62 (0.08 mu g/side), given 0 h after training, or an intrahippocampal infusion of the protein kinase A inhibitor, KT5720 (0.5 mu g/side), gi ven 3 h after training. Pretest ip injections of ACTH (0.2 mu g/kg) or vasopressin (10.0 mu g/kg), but not saline, reversed the amnesia caus ed by beta-endorphin and ECS but not that caused by the enzyme inhibit ors. This suggests that the amnesia produced by intrahippocampal KN62 and KT5720 administration is stronger than that caused by ECS and beta -endorphin, possibly because the former interfere directly with specif ic steps of the core biochemical chain of events that underlies memory consolidation. (C) 1997 Academic Press.