title: Effects of crotoxin on autonomic neuromuscular transmission in the guinea-pig myenteric plexus and vas deferens.
abstract: The effects of crotoxin, the neurotoxic complex from the venom of the South American rattlesnake Crotalus durissus terrificus on mammalian autonomic neuromuscular transmission, have been investigated. In the longitudinal muscle of the guinea-pig ileum, crotoxin induced a dose-dependent contraction which was followed by relaxation, in spite of the continued presence of the toxin. The contractile response was inhibited by indomethacin, tetrodotoxin, verapamil or nifedipine, but was unaffected by atropine, propranolol, mepyramine or methysergide. In addition, crotoxin caused a presynaptic inhibition of the electrically-evoked twitch of the longitudinal muscle of the guinea-pig ileum. In the guinea-pig vas deferens crotoxin also caused an inhibition of the response to field stimulation. The inhibition was reversible after washing and the preparation remained insensitive to further doses of the toxin. The inhibitory effects of crotoxin were not mediated by noradrenaline and were not due to a non-specific smooth muscle depression, because it was not associated with any reduction in motor responses to acetylcholine, ATP, bradykinin or substance P. Pre-incubation of the guinea-pig vas deferens with indomethacin blocked the inhibitory effects of the toxin. This suggests that the presynaptic activity of crotoxin in the vas deferens might be mediated by prostaglandins.
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects*; D003435:Crotalid Venoms / Q000633:toxicity*; D003439:Crotoxin / Q000633:toxicity*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009197:Myenteric Plexus / Q000187:drug effects; D010275:Parasympathetic Nervous System / Q000187:drug effects; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012110:Reserpine / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D003435:Crotalid Venoms; D012110:Reserpine; D003439:Crotoxin; D011433:Propranolol; D007213:Indomethacin; D010646:Phentolamine