5-HT and α-m-5-HT attenuate excitatory synaptic transmissions onto the lateral amygdala principal neurons via presynaptic 5-HT1B receptors

Accumulating evidence suggests that the serotonergic (5-HT) system in the amygdala has significant effects on affective states. Dysregulation of the 5-HT system in the basolateral amygdaloid complex causes affective disorders. To search for therapeutic targets, subtype specification of 5-HT receptors is crucial. The present study was undertaken to identify the 5-HT receptor subtype responsible for the 5HT-mediated suppression of excitatory transmission to principal neurons (PNs) in the lateral amygdala (LA). Whole-cell recordings were performed to record excitatory post synaptic currents (EPSCs) in acute rat brain slices. We confirmed that 5-HT and alpha-m-5-HT, a broad 5-HT2 receptor agonist, attenuated EPSCs in LA PNs. The extent of suppressions by 5- HT and alpha-m-5-HT remained unchanged in the presence of ritanserin, a broad 5-HT2 receptor antagonist. In the presence of NAS-181, a selective 5-HT1B receptor antagonist, the extent of EPSC suppressions by 5-HT and alpha-m-5-HT was diminished. CP93129, a selective 5-HT1B receptor agonist, attenuated EPSCs in LA PNs, and this effect was abolished in the presence of NAS-181. Additionally, the paired-pulse ratio of EPSCs was increased by CP93129. Thus, our results indicate that 5-HT and alpha-m-5-HT attenuate excitatory transmissions to LA PNs via presynaptic 5-HT1B receptors. (C) 2022 Elsevier Inc. All rights reserved.

Automated summary

Accumulating evidence suggests that the serotonergic system in the amygdala plays a significant role in affective states. This study aimed to identify the specific subtype of 5-HT receptors responsible for modulating excitatory transmission in the lateral amygdala. The results show that 5-HT1B receptors are involved in the attenuation of excitatory synaptic currents in principal neurons of the lateral amygdala.