Substance P-like immunoreactivity in the rabbit inner ear

The auditory and vestibular sense-organs of the rabbit were examined for the presence of substance P(SP) by an immunohistochemical technique using a monoclonal SP-antibody. Between 30 and 40 per cent of the cells of the vestibular ganglia and about 50 per cent of the spiral ganglion cells innervating the extreme basal part of the cochlea showed SP-like immunoreactivity. The neural elements in the vestibular sensory epithelia, notably the calyx-formed nerve terminals of type I sensory cells of the maculae, also showed strong SP-like immunoreactivity. The findings suggest the possibility of a modulator or transmitter role for SP in the inner ear function.