Glutamate as the transmitter at fast and slow neuromuscular junctions of larval diptera

Summary Excitatory postsynaptic currents (EPSCs) produced by stimulating either the fast or slow motor axon to the bodywall muscles of larval sheepfly, are reduced by 60% in the presence of 2 × 10^–4 M L-glutamate. L-aspartate at 2 × 10^–4 M is without effect on either the fast or slow EPSC. Extracellularly recorded slow EPSCs are also reduced by iontophoresis of L-glutamate onto the active site. Iontophoresis of L-aspartate has no effect on the slow EPSC. These results are discussed in relation to a possible transmitter role for glutamate and aspartate at fast and slow excitatory neuromuscular synapses of the bodywall muscles of larval sheepfly.Abbreviation EPSC excitatory postsynaptic current The author is indebted to Professor P.N.R. Usherwood for use of facilities and for helpful discussion during the course of this work. The author is supported by the S.R.C.