Exposure to nerve does not affect the appearance of calcium currents in embryonic muscle.

Xenopus skeletal muscle cells in culture develop two inward calcium currents, a slow and a transient current, which differ in terms of kinetics, voltage of activation and sensitivity to nifedipine. The slow current was present in many cells by the first day in culture and in all the cells by the second day in culture. In contrast, the transient current was present in only a small proportion of cells on the first day and in the majority of cells by the fifth day. We found that neither the characteristics of the two currents nor the developmental sequence of their appearance were altered by the presence or absence of nerve or by a prior exposure to nerve in-vivo.