Expression of choline acetyltransferase activity in a co-culture of spinal cord and skeletal muscle cells is inhibited by myogenic differentiation inhibitors.

The effect of myogenic differentiation on the expression of choline acetyltransferase (ChAT) activity in co-cultured spinal cord neurons was studied. ChAT activity in spinal cord cells dissociated from 14-day mouse embryos was markedly increased when co-cultured with skeletal myotubes from 20-day embryos. This enhancement of ChAT activity was not observed in the presence of concanavalin A (ConA) or N-methyl-1-deoxynojirimycin (MDJN) which inhibits myoblast fusion, creatine phosphokinase and acetylcholinesterase activities in muscle cells. ChAT activity in spinal cord neurons cultured alone was unaffected by these agents. The inhibitory effect of ConA and MDJN was reversible, with an almost full recovery of ChAT activity following removal of the agents. Addition of ConA or MDJN after myotube formation exerted little inhibitory effect on ChAT activity. The effects of ConA and MDJN on ChAT activity in co-cultures were comparable to those on creatine phosphokinase and acetylcholinesterase. These observations indicate that the neurotrophic effects of skeletal muscle cells on spinal cord neurons are dependent on the differentiation state of the muscle cells.