EFFECTS OF ACTH AND ACTH-4-10 ON AVERSIVE MEMORY RETRIEVAL IN RATS

The aim of the study was to examine whether ACTH and ACTH-fragment 4-1 0, given before the test would produce a selectively enhanced retrieva l of aversive memories, in the same way as preexposure to inescapable footshocks, in rats. For this purpose animals conditioned in a T-maze with appetitive (10% sucrose) and aversive (2.0 mA footshock) events w ere administered (s.c.) a single dose of 10, 20 or 40 ug/rat of ACTH o r 5, 10 or 20 ug/rat of ACTH-fragment 4-10, 20-min before testing. The retention test conducted in the same training apparatus 72-hrs after conditioning showed a dose-dependent increase in latencies to enter th e previously shocked goalarm with the absence of such a difference in responding to the nonshocked goalarm, in ACTH and ACTH 4-10 treated gr oups. This differential response was not observed in saline treated ra ts. This effect of peptides on memory retrieval was similar to that se en following inescapable footshock in rats. The results suggest the po ssible involvement of ACTH in the differential enhancement of memory o f helplessness condition.