Effects of activation and inactivation of glucocorticoid receptors of basolateral amygdala on fear memory extinction in rats

  Introduction: Glucocorticoid receptors (GRs) of basolateral amygdala (BLA) play an important role in emotional learning and memory. The aim of present study was to determine the role of GRs of BLA in extinction of fear memory in inhibitory avoidance learning (PAL) in rats.   Materials and Methods: Rats with surgically implanted bilaterally cannulae aimed at the BLA were trained and tested in an inhibitory avoidance task. Animals received bilateral microinjections of corticosterone (CORT, 0.3 or 3ng/0.5µl per side), RU38486 (0.3 or 3 ng/10.5µl per side /side) or combinenation of both drugs into BLA 30 min before the first retrieval test which was done 2 days after training. Memory retention again tested 2, 9, 12, 14 and 16 days after the first retention test, during which the latency to re-enter dark compartment of the apparatus was recorded.   Results: Results indicated that microinjections of both CORT and RU38486 and also their combination into BLA facilitated the extinction of fear memory.   Conclusion: It seems that GRs located in the BLA nucleus play a critical role in fear memory extinction.