title: alpha-latrotoxin of black widow spider venom depolarizes the plasma membrane, induces massive calcium influx, and stimulates transmitter release in guinea pig brain synaptosomes.
abstract: The effect of alpha-latrotoxin from black widow spider venom upon guinea pig cerebral cortical synaptosomes is described. Plasma membrane potential (delta psi p), in situ mitochondrial membrane potential (delta psi m), Ca2+ transport, gamma-amino[3H]butyrate release, [3H]noradrenaline release, and synaptosomal ATP were monitored under parallel conditions. Potentials were determined both isotopically and with a tetraphenylphosphonium-selective electrode. alpha-Latrotoxin depolarizes delta psi p selectively, both in the presence and absence of Ca2+. A slight toxin-induced depolarization of delta psi m is a consequence of a massive Ca2+ uptake across the plasma membrane. Depolarization of delta psi p is insensitive to tetrodotoxin, and Ca2+ entry is only partially inhibited by verapamil. Release of [3H]noradrenaline and gamma-amino[3H]butyrate is markedly stimulated by the toxin in the presence of Ca2+, and this effect is only slightly reduced in Ca2+-free conditions.
mesh_terms: D000818:Animals; D001180:Arthropod Venoms / Q000494:pharmacology*; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000187:drug effects*; D008928:Mitochondria / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D013111:Spider Venoms / Q000494:pharmacology*; D013574:Synaptosomes / Q000378:metabolism / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D001180:Arthropod Venoms; D009498:Neurotoxins; D013111:Spider Venoms; D005680:gamma-Aminobutyric Acid; C020763:alpha-latrotoxin; D014700:Verapamil; D002118:Calcium; D009638:Norepinephrine