Postsynaptic inhibition underlying spike suppression of secondary vestibular neurons during quick phases of vestibular nystagmus

Synaptic mechanisms of spike suppression of vestibular neurons during quick phases of vestibular nystagmus were investigated by intracellular recording in the rostrolateral part of the cat medial vestibular nucleus. When repetitive spike discharges of vestibular neurons were abruptly suppressed at the quick phase, the membrane potential shifted steeply in the hyperpolarizing direction. After the commissural IPSP was inverted into depolarization by intracellular injection of Cl^? ions, the hyperpolarizing deflection of the membrane potential at the quick phase was also inverted into a depolarizing potential. The results indicate that an abrupt generation of IPSPs in vestibular neurons underlies the quick phase suppression of spike activity in these neurons.