In vitro reconstitution of signal transmission from a hair cell to the growth cone of a chick vestibular ganglion cell

Abstract

Signal transmission from a chick hair cell to the growth cone of a vestibular ganglion cell was examined by placing an acutely dissociated hair cell on the growth cone of a cultured vestibular ganglion cell. Electrical stimuli were applied to the hair cell while monitoring the intracellular Ca2+ concentration ([Ca2+]i) at the growth cone or recording whole-cell currents from the vestibular ganglion cell. Electrical stimulation of the hair cell induced [Ca2+]i increases at the growth cone and inward currents in the vestibular ganglion cell. The [Ca2+]i increase was blocked by 6-cyano-7-nitroquinoxaline (CNQX) (10 μM) but not by 2-amino-5-phosphonovaleric acid (APV; 50 μM). Glutamate (100 nM–300 μM) applied to the vestibular ganglion cell by the Y-tube method induced inward currents which were also antagonized by CNQX, but not by APV. These results indicate that the electrical stimulation of a hair cell induced glutamate or glutamate like agent release from the hair cell, which activated non-N-methyl-d-aspartate receptors at the growth cone of the vestibular ganglion cell, followed by action potentials and [Ca2+]i elevation in the vestibular ganglion cell. This is the first demonstration of in vitro reconstitution of functional signal transmission from a hair cell to a vestibular ganglion cell.