Subcellular immunolocalization of NMDA receptor subunit NR-1 in the chinchilla vestibular periphery

The immunohistochemical localization of N-methyl-D-aspartate (NMDA) glutama te receptor subunit, NR-1 was investigated in the chinchilla cristae ampull aris and utricular maculae at the light and electron microscopy level with the use of specific antipeptide antibodies. The afferent calyces that inner vate type I hair cells, and the basolateral type I vestibular hair cell is NR-1 immunoreactive. The afferent boutons innervating type II hair cells an d the basal portion of type II hair cell are NR-I non-immunoreactive. These findings are consistent with NMDA receptor mediation of afferent excitator y neurotransmission from type I, but not type II hair cells to the primary afferent vestibular nerve. The NMDA receptors on the type I hair cell are l ocated in areas of synaptic specialization, and may play a role in autoregu lation. The localization of the NMDA receptor subunit in type I but not typ e ii hair cells is intriguing. (C) 1999 Elsevier Science B.V. All rights re served.