Effect of posttraining injections of glucocorticoid agonist and antagonist into the dorsal hippocampus on spatial memory storage in place avoidance learning task

Introduction. T he presen t ex periment exam ined th e effec t of posttraining injections of glucocorticoid ago nist and a ntagonist into th e dorsal hippocamp us (DH) o n re te nt ion of spa tia l memory in p lace avoida nce lea rn ing task. Materials and Methods. Ma le Long-Eva ns strai n rats wer e surgically implanted bi late ra lly with cannu lae a imed at the DH a nd were train ed to avoid a f,O degree segment of th e are na en tering which was punished by mild fnotsh ock. Pla ce avo ida nce tra in ing occu rred in a singl e 30-min sess ion a nd th e avo ida nce memory was assess e e! duri ng a 30-min extinctio n tr ial 24 h later. T he time to the first e ntry a nd th e num ber of entran ces into the p unished sector d ur ing extinctio n we re use d to me asure the place avoida nce memory. Dexame th asone (0. 1 ,u g/O,(~u J, pe r side ) as a glucocort ico id agonist and RU384486 (3 ng/0.6 ,ul pe r s ide ) as a gluco corticoid antagonist were inject ed bilaterally int o DH immediate ly and 60 and J20 min a fte r trai ning. Re tentio n test was doneone days later. Results. Results indicated that infusio n of glu coc ortico id ago nist a nd antagonist immed iately a nd 60 min but not 120 min afte r tr aining into DH significa ntly e nhanced and impa ired ret e ntion pe rformance, respective ly. Conclusion. T he above results show that glucocorticoid receptor plays a n important ro le in consolidation of sp atial memory in place avoidance learni ng at least 60 min afte r training.