title: Joro spider venom: glutamate agonist and antagonist on the rod retina of the dogfish.
abstract: The venom of the Joro spider, reported to block glutamate action selectively at some glutaminergic synapses, was applied focally to rod horizontal and on-bipolar cells in dark-adapted retinal slices. The venom hyperpolarized horizontal cells in the dark and blocked their responses to light. Depolarization of horizontal cells by ionophoretic pulses of L-glutamate, L-aspartate or kainate was antagonized by the toxin in a slowly reversible manner. These results are consistent with other evidence for glutamate as the rod neurotransmitter acting on a single postsynaptic receptor type on horizontal cells. In contrast, the venom, like glutamate, closed the same ion channels of on-bipolar cells as the transmitter, thereby blocking light responses of on-bipolars. Joro spider toxin distinguishes the glutamate receptor-channel complexes of rod horizontal and on-bipolar cells.
mesh_terms: D000818:Animals; D001180:Arthropod Venoms / Q000494:pharmacology*; D001224:Aspartic Acid / Q000494:pharmacology; D004284:Dogfish; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D007478:Iontophoresis; D007608:Kainic Acid / Q000494:pharmacology; D010775:Photic Stimulation; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000378:metabolism; D012160:Retina / Q000187:drug effects*; D013111:Spider Venoms / Q000494:pharmacology*; D013112:Spiders
chemical_list: D001180:Arthropod Venoms; D005971:Glutamates; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D013111:Spider Venoms; D001224:Aspartic Acid; D018698:Glutamic Acid; D007608:Kainic Acid