The role of basolateral amygdala adrenergic receptors in hippocampus dependent spatial memory in rat

Background and the purpose of the study: There are extensive evidences indicating that the noradrenergic system of the basolateral nucleus of the amygdala (BLA) is involved in memory processes. The present study investigated the role of the BLA adrenergic receptors (ARs) in hippocampus dependent spatial memory in place avoidance task in male rat. Material and Methods: Long Evans rats (n = 150) were trained to avoid footshock in a 60 degrees segment while foraging for scattered food on a circular (80-cm diameter) arena. The rats were injected bilaterally in the BLA specific ARS (Adrenergic receptors) agonist norepinephrine (NE, 0.5 and 1 mu g/mu l) and specific beta-ARs antagonist propranolol (PRO, 0.5 and 1 mu g/mu l) before acquisition, after training or before retrieval of the place avoidance task. Control rats received vehicle at the same volume. 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. Results: Acquisition and consolidation were enhanced and impaired significantly by NE and PRO when the drugs were injected 10 min before or immediately after training, respectively. In contrast, neither NE nor PRO influenced animal performances when injected before retention testing. Conclusion: Findings of this study indicates that adrenergic system of the BLA plays an important role in regulation of memory storage and show further evidences for the opinion that the BLA plays an important role in integrating hormonal and neurotransmitter influences on memory storage.