DEVELOPMENTAL-CHANGE IN THE MODULATION OF ACETYLCHOLINE-RECEPTOR CHANNEL BY PROTEIN-KINASE-C ACTIVATION IN XENOPUS EMBRYONIC MUSCLE-CELLS

Protein phosphorylation is important in synaptic transmission and plasticity. We report here that phorbol 12-myristate 13-acetate (TPA), a protein kinase C (PKC) activator, enhances the postsynaptic response at developing neuromuscular junctions by increasing the open time of embryonic acetylcholine (ACh) channels at earlier stages of cultured myocytes. Compared with day-1 cultures, the effects of TPA declined or disappeared on day-3 cultures. Adenosine 5'-triphosphate (ATP) which is co-stored and co-released with ACh at motor nerve terminals and is reported to enhance spontaneous synaptic currents by the activation of PKC, also shows similar developmental changes in the modulation of embryonic ACh channels in Xenopus embrydnic myocytes.