Résumé
The level of acetylcholine receptor α-subunit mRNA in primary cultures of chicken myotubes increases when the spontaneous electrical activity of the myotube is suppressed by the sodium channel blocker tetrodotoxin. This increase was prevented by two translational inhibitors: cycloheximide and anisomycin. Neither the basal level of α-subunit mRNA nor that of muscle-specific creatine phosphokinase mRNA was affected by these inhibitors. In contrast, cycloheximide potentiated the limited increase of α-subunit mRNA levels evoked by the neuropeptide calcitonin gene-related peptide. The high level of α-subunit mRNA elicited by tetrodotoxin treatment did not persist after subsequent addition of cycloheximide in the presence of tetrodotoxin, indicating that the continuous synthesis of protein factor(s) is necessary for this regulation. Moreover, cycloheximide decreased the high level of α-subunit mRNA present at early stages of in vitro maturation of muscle primary cultures without blocking the further increase of the muscle-specific creatine phosphokinase mRNA. Implications of the requirement for constant synthesis of protein factors on the induction of muscle-specific gene expression by blocking myotube electrical activity are discussed.