SEROTONERGIC INNERVATION OF THE ORGAN OF CORTI OF THE CAT COCHLEA

THE presence and distribution of serotonin-containing fibers within th e adult cat cochlea is reported here for the first time. The 5-HT-like immunoreactive fibers were mainly found in the middle coils of the ca t cochlea, following a peripheral distribution similar to that of the olivocochlear lateral efferent system (OLES). Thus, 5-HT-like immunore active varicose fibers were found within the intraganglionic spiral bu ndle, the inner and the tunnel bundles, although, some variation with the distribution of other neuroactive substances of the OLES were obse rved. In particular, some isolated fibers from the tunnel bundle branc hed towards the first row of the outer hair cells. Cochlear serotonerg ic fibers might be involved in the auditory processing within the coch lea as efferent modulating fibers.