Identification of voltage-sensitive calcium channels in Setaria cervi (Nematoda: Filarioidea) and their role in regulation of spontaneous motility.

ABSTRACT

Whole worm of Setaria cervi and its nerve muscle preparation exhibit rhythmical movements when suspended in modified Ringer's solution in an isolated organ bath. Deprivation of calcium from the bathing fluid results in gradual reduction in the amplitude and rate of contraction till the movements ceased completely. Similar results were obtained by adding EDTA (5 micrograms/ml) to the bath. The effect was concentration related and was evident early with higher concentration of EDTA. Acetylcholine which increases spontaneous movements of the whole worm as well as N.M. preparation failed to do so when the movements were inhibited either in calcium free solution or in the presence of EDTA. Addition of calcium channel blocker, Nifedipine to the bathing fluid also resulted in concentration related reduction of movements of the preparation of Setaria. Further, the stimulant response of Ach was also reduced by Nifedipine and this too was related to the concentration of calcium channel blocker in the bath. The evidence clearly indicates that presence of calcium is essential for the stimulant response of Ach on S. cervi, which like mammalian tissues contain calcium channels that can be blocked by specific blocking agents.