PROPERTIES OF LARVAL NEUROMUSCULAR-JUNCTION IN DROSOPHILA-MELANOGASTER

The anatomy and physiology of the Drosophila larval neuromuscular junction were studied. The dependence of muscle resting potentials on [K+]0 and [Na+]0 follows the Goldman-Hodgkin-Katz equation (PNa/PK = 0.23). Cl- distributes passively across the membrane. The mean specific membrane resistance of muscle fibers is 4.3 .times. 103 .OMEGA. cm2, and the mean specific membrane capacitance is 7.1 .mu.F[Faraday]/cm2. The muscle fiber is virtually isopotential. Transmitter release is quantal. Both the miniature excitatory junctional potential and the evoked release follow the Poisson distribution. Transmitter release depends on approximately the 4th power of [Ca2+]0. If Sr2+ replaces Ca2+, it depends on approximately the 4th power of [Sr2+]0. Mg2+ reduces transmitter release without altering the 4th power dependence on [Ca2+]0.