Synapse formation and synaptic activity in mammalian nerve-muscle co-culture are not inhibited by antibodies to neural cell adhesion molecule L1.

Co-cultures of rat myotubes and spinal cord explants from mouse embryos were maintained in the presence of Fab fragments of polyclonal antibodies to neuronal cell surface antigen L1. Microscopic observation showed that neurite outgrowth was not blocked by anti-L1. By intracellular recording, no effect was observed on the number of myotubes that showed endplate potentials, nor on the efficiency of synaptic contacts. As was demonstrated by indirect immunofluorescence, added Fab fragments remained bound to the neurite surface and were present in the medium for at least two days in culture, after which time antibodies were replaced during the medium change. Taken together, these observations show that L1 antigen is not involved in synapse formation between nerve and muscle.