Effects of glycine on the spontaneous activity of medial vestibular nucleus (MVN) neurons recorded extracellularly from guinea-pig brainstem slices were investigated. Glycine produced a dose-dependent decrease in the resting discharge rate of all MVN neurons tested, with a mean EC50 of 3.9 x 10(-4) M. The inhibitory effect of glycine was reversibly blocked by strychnine and persisted in a low calcium/high magnesium-containing saline solution. These findings suggest the existence of a direct strychnine-sensitive inhibitory effect of glycine on guinea-pig MVN neurons.