L-Glutamate at Insect Excitatory Nerve–Muscle Synapses

Abstract

THE release of acetylcholine from vertebrate motor nerve terminals has been demonstrated several times since the original observation by Dale and his colleagues in the 1930s, and identification of acetylcholine as the transmitter at vertebrate nerve–muscle synapses now seems well established. At locust and grasshopper muscle synapses, however, where acetylcholine has no pharmacological action^1,2, it has been suggested that L-glutamate mediates transmission at excitatory synapses^3–5 and γ-aminobutyric acid mediates transmission at inhibitory synapses^3,6. This communication reports studies on the release of glutamate from endings of peripheral excitatory axons (motor axons) in the locust, Schistocerca gregaria. The effects of iontophoretic application of L-glutamate to locust muscle fibres have also been studied in an attempt to pinpoint the site or sites of action of this substance.