Serotonergic innervation of the auditory midbrain: dorsal raphe subregions differentially project to the auditory midbrain in male and female mice

AbstractIn the auditory inferior colliculus (IC), serotonin reflects features of context including the valence of social interactions, stressful events, and prior social experience. However, within the dorsal raphe nucleus (DRN; B6  + B7), the source of serotonergic projections to the IC has not been resolved at the level of DRN subregions. Additionally, few studies have investigated which DRN subregions are engaged during naturalistic, sensory-driven social behaviors. We employ traditional, retrograde tract-tracing approa ches to comprehensively map the topographic extent of DRN-IC projection neurons in male and female mice. We combine this approach with immediate early gene (cFos) mapping in order to describe the functional properties of DRN subregions during contexts in which serotonin fluctuates within the IC. The se approaches provide novel evidence that the dorsal (DRd) and lateral (DRl) B7 subregions are primarily responsible for serotonergic innervation of the IC; further, we show that this projection is larger in male than in female mice. Additionally, DRd and the ventral B7 (DRv) contained more transcri ptionally active serotonergic neurons irrespective of behavioral context. Male mice had more active serotonergic neurons in DRd and DRv than females following sociosexual encounters. However, serotonergic activity was correlated with the expression of female but not male social behaviors. The topogr aphic organization of the DRN-IC projection provides the anatomi...

Source: Anatomy and Embryology - June 18, 2020 Category: Anatomy Source Type: research