hospholipase C-mediated inhibition of the M-potassium current by uscarinic-receptor activation in the vestibular primary-afferent eurons of the rat

The activation of the efferent vestibular systemmodifies the basal discharge and the dynamic response of primary-afferent neurons to headmotion and gravitational stimuli. The efferent input to afferent neurons is mediated primarily by cholinergic synapses that activate both muscarinic and nicotinic receptors. Previously we had shown that themuscarinic-acetylcholine-receptor (mAChR) activationmodulates the low-voltage-activated M-type potassium current (IK,M) in the vestibular-afferent neurons. In this work we studied the second-messenger system mediating the inhibition of IK,M after mAChR activation. For this, voltage and current-clamp recordings were obtained in the cultured vestibular-afferent neurons of the rat. The IK,M was measured during its deactivation. Response to current-pulse injection was also studied. The use of the mAChR agonist oxotremorine-M significantly reduced the amplitude of the IK,M andmodified the discharge response to current pulses from single spike tomultiple spiking, reducing the