Effects of felodipine and verapamil on transmission in the isolated superior cervical ganglion of the rat.

The effects of Ca2+ channel blockers verapamil and felodipine on transmission in the isolated superior cervical ganglion and conduction in the cervical sympathetic nerve trunk of the rat were examined by recording compound postganglionic action potentials as indexes of ganglionic transmission. Both verapamil and felodipine blocked ganglionic transmission but only at high concentrations, verapamil being more effective in this regard than felodipine. Increasing (from 2.2 to 4.4 mM) or decreasing (from 2.2 to 0.4 mM) Ca2+ concentration did not significantly affect the inhibitory action of these agents. Neither agent had any significant effect on conduction of compound action potential along the preganglionic cervical sympathetic nerve trunk. The results suggest that the observed ganglionic blocking effects of these drugs are apparently unrelated to Ca2+ channel blockade.