Neurophysiological correlates of the dopaminergic cilio-inhibitory mechanism of Mytilus edulis.

The neurophysiological regulation of gill ciliary activity by the CNS of the bivalve mollusc Mytilus edulis was studied by recording electrophysiological activity of the branchial nerve while simultaneously observing ciliary activity of the lateral ciliated cells of the gill by stroboscopic microscopy. The addition of dopamine to the visceral ganglion slowed and stopped ciliary activity by increasing the firing rate of the cilio-inhibitory dopaminergic neurones of the visceral ganglion which innervate the gill. This could be antagonized at the ganglion by pre-applications of ergonovine or methysergide, or by prior treatments of intact animals with the neurotoxin 6-hydroxydopamine. The study confirms earlier work showing the inhibitory functioning of dopaminergic neurones of the CNS and demonstrates the manner in which they may exert their effects.