Wide Range Transmitter Sensitivities of a Crustacean Chloride Channel

Abstract

Crustacean neuromuscular junctions use glutamate as the excitatory transmitter and GABA as the inhibitory transmitter. Excitatory, glutamate-activated channels have been studied in locust and crayfish by recording single channel currents (Patlack et al., 1979; Cull-Candy et al., 1980; Franke et al., 1983). Recently, the recording technique has been improved to the point at which GΩ-seals can be obtained, and these have been used to characterize the excitatory, glutamate-activated channels in muscle fibers of crayfish (Franke et al., 1987; Hatt et al., 1988a) and locust (Dudel et al., 1988). The channel has a high conductance of about 100 pS and single openings are very short: on the average 0.2 to 0.3 ms. At high glutamate concentrations, channel openings are grouped in bursts, the number of openings per burst and burst duration increasing when glutamate concentration rises from 0.2 to 10 mM. The channel described above is located at the excitatory synapses of muscle fibers of crayfish.