Electrical Activity of Lymphatic Smooth Muscles

Abstract

Membrane action potentials of bovine mesenteric lymphatics were recorded simultaneously with isometric contractions by the use of the sucrose gap method. The action potentials, about 3 sec in duration, always had one-to-one correspondence to the contraction waves. Each action potential consisted of three phases, i.e., initial slow depolarization, spike, and slow repolarization. The application of nor-adrenalin elicited a slight but long-lasting depolarization superimposed by frequent discharges of action potentials. The administration of acetylcholine in a relatively high concentration to the preparations induced a transient depolarization followed by the occurrence of action potentials. From the effects of tetrodotoxin, manganese, calcium-free environment, and barium chloride on the spontaneous contractions, it was suggested that calcium current may probably play a major role in producing spike discharge in bovine lymphatic smooth muscles.