GATING KINETICS OF THE QUISQUALATE-SENSITIVE GLUTAMATE-RECEPTOR OF LOCUST MUSCLE STUDIED USING AGONIST CONCENTRATION JUMPS AND COMPUTER-SIMULATIONS

Outside-out patches excised from extrajunctional membrane of locust mu scle were subjected to ''concentration jumps'' of L-glutamate, using t he liquid filament switch technique, to study channel opening and clos ing rates, desensitization onset, and recovery from desensitization of a quisqualate-sensitive glutamate receptor (qGluR). Based on data obt ained from these experimental studies, computer modeling techniques ha ve been used in an attempt to simulate the behavior of qGluR during a concentration jump of L-glutamate. A linear model with three closed st ates (one unliganded, one monoliganded, and one biliganded), one open state (binding two molecules of L-glutamate), and two desensitization states (the one monoliganded, the other biliganded) leading from the u nliganded closed state simulated all of the experimentally observed be havior. The results are discussed in the context of previous equilibri um studies in which desensitization was inhibited with concanavalin A and for which a ten-state model was required to simulate the behavior of qGluR.