Synapse repression in cell culture

The phenomenon of synapse repression was investigated in cell culture. It was found that the number of synapses between ciliary ganglion neurons and myotubes was reduced by the concomitant presence of ventral spinal cord neurons. Neurons from dorsal root ganglia, dorsal spinal cord or cortex did not cause a reduction. Conditioned medium from ventral spinal cord-myotube co-cultures was without effect suggesting the absence of soluble 'repression factors'. The addition of D-tubocurarine partially reversed the repression, indicating that the phenomenon has both activity-dependent and activity-independent aspects.