MEMBRANE AND FIRING PROPERTIES OF AVIAN MEDIAL VESTIBULAR NUCLEUS NEURONS IN-VITRO

The intrinsic membrane and firing properties of medial vestibular nucl eus (MVN) neurons were investigated in slices of the chick brainstem u sing intracellular recording and current injection. Avian MVN neurons fired spontaneous action potentials with very regular interspike inter vals. The rapid repolarization of all action potentials was followed b y an afterhyperpolarization. Intracellular injection of steps of hyper polarizing current revealed both an inward rectification of the membra ne potential during the step and a rebound depolarization following th e offset of the step. In some neurons, the rebound depolarization resu lted in bursts of action potentials. Steps of depolarizing current app lied to spontaneously active neurons evoked increases in firing rate t hat were higher at the onset of the step than during the steady-state response. The relationship between current and firing rate was linear. The membrane and firing properties of avian MVN neurons were distribu ted continuously across the population of recorded neurons. These prop erties appear identical to those of rodent MVN neurons, suggesting tha t the composition and distribution of ion channels in the MVN neuronal membrane has been highly conserved across vertebrate species.