GLUCOCORTICOID ANTAGONIST ADMINISTRATION INTO THE BASOLATERAL AMYGDALA MODULATES PLACE AVOIDANCE MEMORY

Abstract

The present study examined the significance of glucocorticoid receptors (GRs) in the basolateral amygdala (BLA) on place avoidance memory in male rats. Rats were trained to avoid footshock in a 60° segment while foraging for scattered food on a circular (80-cm diameter) arena. The rats were injected bilaterally in the BLA with the specific GR antagonist RU 38486 (3 ng dissolved in 1 ul 2% ethanol) before acquisition, after training or before retrieval of the place avoidance task. Control rats were injected with vehicle. The learning in a single 30-min session was assessed 24h later by a 30 min extinction trial in which the time to first entrance and the number of entrances to the shocked area measured the avoidance memory. Acquisition and consolidation were impaired when the drug was injected 10 min before training, immediately after training, or 60 min after training (P<0.01), but not 120 min after training. In contrast, injection of the antagonist before the retrieval test was ineffective (P>0.05). These findings indicate that glucocorticoids affect memory storage at least in part by binding directly to GR in the BLA and provide further evidences for the opinion that the BLA plays an important role in integrating hormonal and neurotransmitter influences on memory storage.