Effects of basolateral and central amygdala lesions on modulation of spatial memory by intrahippocampal injections of glucocorticoid agonist and antagonist

Abstract

Introduction . T he pr esen t experime nt examined th e effect of bilat eral amygda la nuclei lesions o n modulation of spat ia l memory storage indu ced by bilate ra l irura hippocampa l microinfusions of glucocorticoid ago nist a nd a ntagonist in ma le Long-Evan s rats. Material and Methods. Rats were surgica lly impl an ted bilate ra lly with ca nnulae a imed at the dorsa l hippocampus were trained to avoid a 60 segme nt of th e arena e ntering which was punished by mild footshock. Place avoidance tra ining occurred in a single 30-min se ssio n and th e avoida nce memOl);#39 was as sessed during a 30-min extinction tri al 24 hours lat er. The time to the first e ntry a nd the numbers of e ntra nces into th e punished sector during extinction were used to measure the avo idan ce memory. Results. Post -train ing infusio ns of the glucocorticoid receptor agonist (Dexamethaso n) e nha nced spatial place avo ida nce mem ory ret ention and glucocorticoid receptor a ntagonist (RU 3~4~6) impaired this tas k. In both tas ks, ne uro chemically ind uced lesions of the basolateral but not of the ce ntra l amygda la blocked th e memory-mod ulated effects of th e intrahippocampal infusions of the drugs a ffecting the glucocort icoid rece ptors. Conclusion .These findings are consiste nt with pr evious evide nce ind ica t ing tha t th e les ion s of the basola teral amygda la block the memory-modulatory effe cts of systemica lly administered glucocorticoids and provide furth er evide nce tha t the bas o late ra l amygd ala is a critica l area involved in regul ating glucocor ticoid effects in other bra in reg ions involved in memory storage