Potassium and Branchial Nerve Stimulation as Physiologic Regulators of Ciliary Motion in the Bivalve Mytilus Edulis

The lateral cilia(LC) on the gill of the bivalve Mytilus edulis are under neural control. Electrical stimulation (0.1V, 10Hz biphasic, 2msec duration for 3 min) of the branchial nerve(BN) increases the average rate of beating of LC, probably by a mechanism involving the release of 5-hydroxytryptamine (5 HT). Gills previously conditioned with [K]> 30mM enhanced cilioexcitatory effect of exogenous 5-HT.This study investigates the effect of [K] on endogenous neuronal release of 5-HT in intact and severed BN/gill preparations.Gill preparations were isolated and subsequent stroboscopic measurement of LC were made. When nerve stimulation was part of the experiment, the BN was exposed and an electrode placed at its point of departure from the visceral ganglion(VG).For SEM, specimens were doubly fixed in 3% glutaraldehyde in .05 M s-collidine, pH 7.2, for 30 min. washed, and then into Parducz fixative (6 parts of 2% aq. OSO4 to 1 part saturated aq. HgCl2) for 20 minutes. Samples were dehydrated through a graded series of alcohols through 100%, into Freon TF, and critical point dried in Freon 13 in a Bomar 900 EX CPD.