FACTORS AFFECTING THE OPERATION OF GLUTAMATE INDUCED CHANNELS IN LOCUST MUSCLE FIBRES

Abstract

This chapter discusses factors affecting the operation of glutamate induced channels in locust muscle fibers. The analysis of voltage-clamped noise, obtained during ionophoretic application of glutamete to locust nervemuscle junctions, was used to study the mean life-time and the conductance of the synaptic channel. In addition, the analysis of spontaneous miniature excitatory junctional currents (m.e.j.c.s) and nerve-impulse evoked excitatory junctional currents has given information about transmitter-induced channels. These techniques were used to look at factors that affect the kinetics of channels associated with glutamate receptors in the muscle fiber membrane. The mean life-time of the glutamate-induced channel estimated from the spectra is noise (−80 mV) = 2.5 ± 0.13 ms at 20°C. Noise spectra and m.e.j.c.s obtained at various clamp potentials indicate that the lifetime of the glutamate or transmitter operated channel decreases with hyperpolarization. The voltage sensitivity of the channel life-time is somewhat less than, and in the opposite direction to, that previously reported for acetylcholine induced channels in vertebrate endplates.