title: Pharmacological studies on supersensitization. VIII. Dissociation of induction of supersensitivity from presynaptic action of cocaine on isolated vas deferens of guinea pig.
abstract: Effects of cocaine on the isotonic contractions of isolated vas deferens of intact and reserpinized guinea pigs to acetylcholine were examined. Both cocaine-induced increase in sensitivity to acetylcholine and cocaine-induced increase in maximum response of Ca2+-contraction was attenuated remarkably by reserpine. However, cocaine-induced increases in acetylcholine- and K+-contractions in Ca2+-free Tyrode solution were not prevented by reserpine. Acetylcholine-contraction, but not K+-contraction, in the preparation exposed for 5 min to Ca2+-free Tyrode solution were inhibited by reserpine. Cocaine did not inhibit the cholinesterase activity of vas deferens of guinea pig. These results suggested that presynaptic mechanisms of cocaine-induced supersensitivity are excluded and that inhibitory effect of reserpine on cocaine-induced supersensitivity might be due to the inhibition of cocaine-induced increase in calcium-influx into smooth muscle cells of vas deferens.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002802:Cholinesterases / Q000032:analysis; D003042:Cocaine / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D010830:Physostigmine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012110:Reserpine / Q000494:pharmacology; D014439:Tyramine / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D012110:Reserpine; D010830:Physostigmine; D002802:Cholinesterases; D003042:Cocaine; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium; D014439:Tyramine