The effect of calcium-ionophores on acetylcholine release from Schwann cells

Abstract

After denervation of frog [Rana temporaria] muscle, the Schwann cells release multi-molecular amounts of acetylcholine, which evoke miniature endplate potentials in the muscle. The effect of Ca2+ ionophores (X-537 A, A23187 and avenaciolide) and rabbit serum, all of which presumably raise the intracellular level of Ca2+, was examined at normal and denervated endplates. The agents produced a large increase in the release of acetylcholine quanta from nerve terminals. The release of acetylcholine quanta from Schwann cells was greatly depressed. Two systems may be involved in the release of substances from cells. One is activated by a rise in intracellular Ca2+, as in axon terminals; the other is inhibited, as in the Schwann cells.