Acetylcholine promotes progesterone-induced maturation of Xenopus oocytes

Progesterone-induced maturation of follicle-enclosed and denuded Xenopus laevis oocytes was significantly shortened by a concomitant exposure to acetylcholine. The promotion of maturation by acetylcholine was blocked by the specific muscarinic antagonist atropine. The action of acetylcholine was dose dependent, and the neurotransmitter was effective at very low concentrations. Progesterone progressively reduced the electrophysiological responses of X. laevis oocytes to acetylcholine, which completely disappeared close to the time of germinal vesicle breakdown. Progesterone alone did not elicit any electrophysiological responses. The in vitro effect of acetylcholine on oocyte maturation might reflect a physiological influence of the cholinergic system on an in vivo maturation process.