Effects of the suppression of 5-HT receptors in the left, right, or bilateral basolateral amygdala on memory consolidation in chronic stress in male rats.

The serotonin-1A receptors (5-HT) in the two cerebral hemispheres are differentially involved in memory. The distribution of 5-HT receptors in the left and right amygdala is different. Furthermore, evidence shows that the 5-HT receptors in the left and right amygdala work differently in memory function. The basolateral amygdala (BLA) also regulates hippocampal long-term potentiation (LTP) during stress. However, which BLA structure in each hemisphere underlies such lateralized function is unclear. The present research investigated the possible involvement of 5-HT lateralization in the BLA on stress-induced memory impairment. 5-HT receptor antagonist (Way-100-635) was injected into the left, right, or bilateral BLA twenty minutes before chronic restraint stress (CRS) for 14 consecutive days. Results indicated that suppression of 5HT-receptors in the BLA plays an essential role in reducing the acquisition of passive avoidance in the shuttle box test and spatial memory in the Barnes maze test in the stress animals. This decrease was significant in the CRS animals with left and bilateral suppressed 5HT-receptors in the BLA. Field potential recording results showed that the left, right, and bilateral injection of Way-100-635 into the BLA significantly reduced the slope and amplitude of fEPSP in the CA1 area of the hippocampus in stressed rats. No significant difference was observed in neuronal arborization in the CA1 area of the hippocampus. In conclusion, the 5-HT receptor in the left and right sides of BLA nuclei play a different role in memory consolidation in the hippocampus under stress.