Inhibitory effects of atropine and hexamethonium on the angiotensin II-induced contractions of rat anococcygeus smooth muscles.
We have evaluated the interaction between angiotensin II (Ang II) and the cholinergic transmission in anococcygeus smooth muscles isolated from rats treated (sympathectomised group) or not (vehicle group) with reserpine and alpha-methyl-p-tyrosine. For this, we contracted the tissues with Ang II in the presence and absence of atropine and hexamethonium. Ang II induced concentration-dependent contractions, which did not undergo temporal changes in tissues isolated from both groups of rats. In the vehicle group, Ang II induced more potent contractions than in the sympathectomised group. In the sympathectomised rat group, atropine inhibited the contractions induced by Ang II in a concentration-dependent fashion with no decrease in E(max). Additionally, hexamethonium inhibited the contraction induced by Ang II in a concentration-dependent fashion with a decrease in E(max). Association of atropine and hexamethonium produced Ang II-induced curves with rightward shifts from the control curve with a decrease in E(max). Incubation with N(G)-nitro-L-arginine methyl ester (L-NAME) reversed the effects of atropine and hexamethonium association. Conversely, in the vehicle group of rats, atropine and hexamethonium did not produce any significant effect. However, in the presence of yohimbine, atropine shifted the Ang II-induced curves to the right of the control curve with no E(max) decrease. Results suggest that there is a positive interaction between Ang II and cholinergic transmission in the rat anococcygeus smooth muscle mediated by angiotensin receptors located on pre-ganglionic cells.
de Godoy
Márcio Augusto Fressatto
MA
Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Av dos Bandeirantes 3900, 14049-900, Ribeirão Preto, SP, Brazil.
Accorsi-Mendonça
Daniela
D
de Oliveira
Ana Maria
AM
D000804:Angiotensin II / Q000494:pharmacology* / Q000502:physiology; D000818:Animals; D001285:Atropine / Q000008:administration & dosage / Q000494:pharmacology*; D018680:Cholinergic Antagonists / Q000494:pharmacology*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D018738:Hexamethonium / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009388:Neostigmine / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D015016:Yohimbine / Q000494:pharmacology
D018680:Cholinergic Antagonists; D002800:Cholinesterase Inhibitors; D018727:Muscarinic Antagonists; D018733:Nicotinic Antagonists; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D015016:Yohimbine; D009388:Neostigmine; D018738:Hexamethonium; D001285:Atropine; D019331:NG-Nitroarginine Methyl Ester