Effects of concanavalin A on junctional and extrajunctional L-glutamate receptors on locust skeletal muscle fibres

Abstract

1. The effects of the lectin concanavalin A (con A) on the junctional and extrajuctional L-glutamate receptors found on locust extensor tibiae muscle fibres were studied. 2. At concentrations up to 5 × 10 −6 M, topically applied con A did not block junctional or extrajunctional responses evoked by glutamate iontophoresis onto the muscle fibre membrane. 3. At 10 −7 M, con A blocked the desensitization of extrajunctional D-receptors by repeated glutamate pulses, but had no effect on extrajunctional H-receptor desensitization at concentrations up to 5 × 10 −6 M. 4. Con A (10 −7 M) did not alter the glutamate sensitivity of the extrajunctional D-receptor or the sodium dependence of the D-response. 5. At concentrations above 10 −6 M, con A also reduced desensitization of junctional glutamate receptors. 6. The effects of con A on desensitization of junctional receptors and extrajunctional D-receptors was not reversed by washing the preparation in con A-free saline for periods up to 7 hr.