REACTION SCHEME FOR THE GLUTAMATE-ERGIC, QUISQUALATE TYPE, COMPLETELY DESENSITIZING CHANNELS ON CRAYFISH MUSCLE

In analogy with a recently developed reaction scheme for a channel activated by acetylcholine (ACh: nicotinic), we propose a cyclical reaction scheme which agrees with all data published on the completely desensitizing channel type activated by glutamate (Glu) in crayfish muscle. For very high Glu concentrations, desensitization is mainly from the open state, while at lower Glu concentrations desensitization from the singly Glu liganded closed state contributes significantly. The latter pathway and the high Glu affinity of the desensitized channel states account for complete steady-state desensitization of the channel by low Glu concentrations which can occur without any channel opening.