NEUROACTIVE SUBSTANCES IN THE HUMAN VESTIBULAR END ORGANS

In order to evaluate the involvement of neuroactive substances in the human vestibular periphery, the immunocytochemical distribution of sub stance P (SP), calcitonin gene-related peptide (CGRP), and choline ace tyltransferase (ChAT) was examined. SP-like immunoreactivity (LI) was present around and beneath sensory hair cells, probably corresponding to their afferent nerve endings. SP-LI was found predominantly in subp opulations of the primary afferents distributed in the peripheral regi on of the end organs. ChAT-LI and CGRP-LI were found throughout as sma ll puncta below the hair cell layer, probably corresponding to efferen t endings. The present results indicate that these neuroactive substan ces, previously described in animals, are also distributed in the huma n vestibular periphery, and almost certainly contribute to human vesti bular function.