Distribution of serotonin immunoreactivity in the spiral ganglion neurons of mouse cochlea

SummaryObjectiveSerotonin (5-hydroxytryptamine, 5-HT) is a neuromodulator/neurotransmitter with multiple biological functions. Spiral ganglion cells in the cochlea are the primary neurons of the afferent system in the auditory transmission. In this study, we used the immunohistochemical technique to investigate the distribution of serotonin in the spiral ganglion of mouse cochlea.Materials and methodsThe cochlea tissue of four adult mice was dissected and fixed. The immunohistochemical staining was applied by using goat anti-serotonin polyclonal antibody as primary antibody. Tissue sections were treated with biotin-labeled rabbit anti-goat immunoglobulin G, followed by adding streptavidin–biotin–peroxidase complex. Finally, the sections were stained with 3,3-diaminobenzidine (DAB) solution.ResultsThe spiral ganglion exhibited pronounced immunoreactivity for serotonin. Specifically, serotonin immunoreactivity was detected in the cytoplasma of spiral ganglion neurons located in Rosenthal's canal of the bony modiolus of mouse cochlea.ConclusionsSince spiral ganglion neurons are the afferent neurons to the auditory sense organ, our result strongly suggests that serotonin molecule may function as a neuromodulator/neurotransmitter in the peripheral auditory processing.