ONTOGENY OF SUBSTANCE-P IN THE RAT PERIPHERAL VESTIBULAR SYSTEM

Ontogenesis of substance P (SP) in rat vestibular receptors between ge stational day 17 (GD 17) and postnatal day 17 (PD 17) was investigated by immunocytochemistry. SP immunoreactivity was first detected in the afferent nerve fibers of the utricular and saccular maculae on GD 19 and thereafter at birth (PD 0) in the cristae. SP immunoreactivity pre sented a characteristic pattern. It was strictly confined to the slope s of cristae and peripheral regions of the maculae. The pattern of SP immunoreactivity changed during the maturation of the afferent innerva tion pattern between PD 4 and PD 9, resulting in fewer fibers being st ained. Then, the number of immunostained calyces and small bouton endi ngs increased. On PD 17 the distribution of SP was similar to that of the adult stage. We suggest that SP, present in the epithelium at crit ical stages of development, may be involved in the maturation of vesti bular receptors. (C) 1997 Elsevier Science B.V.