Early events of chemical transmission of newly formed neuromuscular junctions in monolayers of human muscle cells co-cultured with fetal rat spinal cord explants.
Early events of chemical transmission were examined in our newly established heterotypic co-culture system with human muscle in monolayer and fetal rat spinal cord explants with attached dorsal root ganglia. The mean amplitude, frequency, rise time and half-fall time of miniature end-plate potentials (MEPPs) were 1.04 mV, 3.9/s, 6.1 ms and 54.9 ms, respectively. Time intervals between successive MEPPs were exponentially distributed. Stimulus evoked potentials were successfully obtained. The distribution of stimulus evoked end-plate potential (EPP) amplitudes was approximately equal to a Poisson distribution. This is the first report concerning intracellular recordings of chemical transmission of developing neuromuscular junctions in heterotypic co-culture system using human muscle. In this co-culture system, the heterotypic neuromuscular junctions show significant similarities previously to those observed in nerve-muscle tissues co-cultured from the same species as well as immature nerve-muscle synapses in situ.