[Argiopine, argiopinines and pseudoargiopinines--blockers of the glutamate receptors in hippocampal neurons].

Several homologous low-molecular weight compounds were purified from venom of spider Argiope lobata. They selectively blocked ionic currents elicited by glutamate and its agonist kainate in the membrane of isolated hippocampal neurons of rat. Three groups of these compounds--argiopine, argiopinines and pseudoargiopinines, blocked glutamate- and kainate-activated ionic currents in a voltage-dependent manner, acting preferentially on agonist-activated ionic channels. These compounds did not change the Kd values for both agonists. The blocking action was partially reversible for argiopine and poorly reversible for other compounds. Rate constants for the interaction of toxins with membrane receptors were estimated from the dependences of two-component kinetics of the blocking action and its recovery on toxin concentrations. Argiopine, argiopinines and pseudoargiopinines may be useful tools for further electrophysiological and biochemical investigation of the mammalian CNS glutamate receptors.