Regulation of network activity in the amygdala by distinct classes of antidepressants

The amygdala as part of the limbic system is a brain structure which lies in the anterior medial portion of each temporal lobe. Through a large variety of connections with brain regions involved in the processing and expression of emotions, the amygdala is thought to be one of the brain's key structures in coordinating these processes. The amygdaloid complex is composed of several nuclei, such as the central nucleus (CeA) or the lateral nucleus (LA), which are interconnected for computation of polymodal sensory information. The LA represents a major input region, whereas the CeA can be seen as the main output region. In the context of psychiatric research, alterations in neural signal propagation through the amygdala most likely are causally involved in the manifestation of affective disorders. To investigate whether different classes of antidepressants (SSRI, TCA, and SSNRI) affect the strength of signal propagation within the amygdaloid complex, we developed high-speed voltage-sensitive dye imaging (VSDI) assays in mouse brain slices to monitor changes in network excitability in response to pharmacological intervention. Our findings demonstrate clear effects of antidepressants on neuronal network activity on a scale that spans whole nuclei of the amygdaloid complex. These findings are in line with the putative roles of these nuclei in information processing and provide novel insights into the action profile of antidepressants at the neuronal network level.