Effect of acute and subchronic stress on electrical activity of basolateral amygdala neurons in conditioned place preference paradigm: An electrophysiological study.

The basolateral amygdala (BLA) plays a critical role in the neural circuitry of stress and mediates the effects of stress on memory related processes. Moreover, this area has an important role in drug-seeking and relapse of approach behavior to drug-associated cues. Therefore, in the present study, we aimed to investigate the effects of acute and subchronic stress in saline- and/or morphine-treated rats in conditioned place preference paradigm on the neural activity in the BLA. Male Wistar rats were divided into two saline- and morphine-treated supergroups. Each supergroup contained control, acute stress (AS) and subchronic stress (SS) groups. In all of the groups, conditioned place preference paradigm was done and thereinafter the spontaneous firing activity was recorded by in vivo single unit recording for 20min. Results showed that in saline-and/or morphine-treated animals, both AS and SS increased neural activity of projection neurons and this increase in morphine-treated animals was more considerable than that of saline-treated animals. Besides, firing rate of interneurons in both supergroups decreased during AS and SS. Decrease of interneurons activity after application of SS in morphine-treated animals was more than that of saline-treated animals. These finding revealed that both of AS and SS increased firing rate of projection neurons but decreased neural activity of interneurons in the BLA. However, effect of AS and SS on the firing rate of BLA neurons in morphine-treated animals was more remarkable than that of saline-treated animals.