Spider toxin blocks excitatory amino acid responses in isolated hippocampal pyramidal neurons.

Using the 'concentration-clamp' technique we have investigated the action of Joro spider toxin (JSTX), as a specific blocker of glutamate receptor, on freshly isolated rat hippocampal pyramidal neurons. The neurons showed prominent responses to L-glutamate (L-Glu), quisqualate (QA) and kainate (KA) and JSTX blocked completely the both responses. The blocking action of toxin was dose-dependent at the concentrations of toxin between 4.8 X 10(-12) and 4.8 X 10(-8) M, and was remarkably similar in cell to cell trials. The kinetics of blockade was revealed by applying the toxin to the non-desensitizing KA response. We suggest that the JSTX spider toxin may be a valuable tool in ligand binding studies of QA/KA receptors in the central nervous system.