Acetylcholine-induced currents at plasma membrane of the frog oocyte.

Although with remarkable variability, membrane permeability in Rana oocytes can be modified by application of acetylcholine. The experiments were carried out in voltage-clamp conditions. Like in Xenopus, the responses proved to be related to activation of muscarinic receptors operating membrane channels probably selective for Cl-. At differences with Xenopus, the net acetylcholine-induced current showed remarkable deviation from linearity, displaying outward-going rectification. Application of acetylcholine typically produced opening of membrane channels, while in late spring, we observed the opposite effect in several batches of oocytes.