Evaluation of the effects of phenylephrine and prazosin injection into basolateral amygdala on the post-stress experience of memory retrieval in rats

Abstract

The present study explored the effect of α1-adrenergic receptors in the basolateral amygdala (BLA) on memory formation in the hippocampus under repeated stress. Male rats received injections of the α1-adrenergic receptor agonist (phenylephrine) or antagonist (prazosin) bilaterally into the BLA five min before foot-shock stress, and emotional and spatial memory and in-vivo long-term potentiation (LTP) in the Cornu Ammonis (CA1) region of the hippocampus were examined. Foot-shock stress impaired performance in emotional and spatial memory tests. However, it had no significant effect on any of the LTP parameters in the hippocampus. Intra-BLA phenylephrine injection significantly impaired emotional and spatial memory performance in stressed animals. On the other hand, administration of intra-BLA prazosin significantly reduced emotional and spatial memory in the control (intact) animals. Neither of the two drugs had any significant effects on LTP parameters. Prazosin effectively impaired memory in the control, but not in the stressed rats. Stress appears to have suppressed the effect of prazosin, and it seems to be a significantly stronger stimulus than prazosin. Taken together, these findings provide new insights into the effects of α1-adrenergic receptors in the BLA on memory storage, during the stress experience.