title: Functional characterization of acetylcholine receptors and calcium signaling in rat testicular capsule contraction.
abstract: The motor activity of mammalian testicular capsule (TC) contributes to male fertility and infertility, but the acetylcholine receptors related to the contractions induced by cholinergic drugs are poorly known. Indeed to characterize the acetylcholine receptors and cellular signaling by Ca(2+) involved in TC motor activity of rats, the potency of agonists (pD₂) and antagonists (pA₂) of acetylcholine receptors, and effects of Ca(2+) cellular transport blockers on the cholinergic contractions were evaluated. pD₂ values of acetylcholine (5.98) were ten-fold higher than that of carbachol (4.99). Efficacy (Emax) of acetylcholine and carbachol to induce contractions corresponded to 95% and 97% of Emax for KCl, but Emax for nicotine was very low (8% of Emax for KCl). Further, physostigmine did not affect the acetylcholine potency. Contractions induced by acetylcholine or carbachol were antagonized by muscarinic but not nicotinic antagonist. The order of pA₂ values obtained for muscarinic antagonists, namely atropine>4-DAMP>AF-DX116>pirenzepine, corresponded to a typical profile of M3 receptors. Contractions induced by acetylcholine or carbachol were inhibited by blockers of Ca(2+) influx through voltage-dependent calcium channels (nifedipine and Ni(2+)), Ca(2+) reuptake by sarco-endoplasmic reticulum (cyclopiazonic acid) and mitochondria (FCCP). The protein kinase C (PKC) inhibitor chelerythrine only affected the acetylcholine-induced contraction. These results suggest that TC motor activity of rats are mediated mainly by M₃ receptors followed by the increase of cytosolic Ca(2+) concentration regulated by voltage-dependent calcium channels, sarco-endoplasmic reticulum and mitochondria. Furthermore, the differential effects of chelerythrine in the acetylcholine or carbachol-induced contractions are discussed.
authors.affiliation: Department of Pharmacology, Federal University of São Paulo-Escola Paulista de Medicina, 04044-020 São Paulo-SP, Brazil.
authors.forename: Edilson Dantas
authors.initials: ED
authors.lastname: da Silva Júnior
authors.forename: Bruno Palmieri
authors.initials: BP
authors.lastname: de Souza
authors.forename: Juliano Quintela Dantas
authors.initials: JQ
authors.lastname: Rodrigues
authors.forename: Afonso
authors.initials: A
authors.lastname: Caricati-Neto
authors.forename: Aron
authors.initials: A
authors.lastname: Jurkiewicz
authors.forename: Neide Hyppolito
authors.initials: NH
authors.lastname: Jurkiewicz
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D018680:Cholinergic Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011950:Receptors, Cholinergic / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism; D013737:Testis / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
chemical_list: D002121:Calcium Channel Blockers; D018679:Cholinergic Agonists; D018680:Cholinergic Antagonists; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D002217:Carbachol; D000109:Acetylcholine; D002118:Calcium
keywords: Calcium; Cholinergic agonists; Muscarinic acetylcholine receptors; Rat testicular capsule.