Single glutamate-activated channels in locust muscle

Abstract

EVIDENCE indicates that glutamate-activated membrane channels (glutamate channels) are responsible for the post-synaptic potential at insect1 and crustacean2 excitatory neuromuscular junctions. They may also be involved in the regulation of pre- and postsynaptic activity in the central nervous system of vertebrates3,4. Analysis of the current noise produced by application of glutamate to excitatory synapses on locust muscle suggested that glutamate channels have a conductance of about 125 pS and a mean open time of about 2 ms (refs 5, 6). Direct measurements of the currents passing through individual acetylcholine-activated channels (ACh channels) in vertebrate muscle membrane have recently been made. The single channel conductance (about 25 pS) and kinetics correspond well with those inferred from noise analysis7,8. We report here the measurement of the currents passing through individual glutamate channels in locust muscle. The conductance of an open single channel is about 130pS. The gating kinetics are complex, and evidence is given for sudden changes in an individual channel's distribution of open and closed times.