Musearinic agonists-induced responses of isolated bovine coronary artery and their dependence on Ca2+

in this in vitro study, the role of Ca2+ of the acetylcholine and carhachol induced contractions and the effects of L-NAME on the acetykholine-induced contractile responses were investigated. Acetylcholine and carhachol caused dose-dependent and reproducible contractions in thiş tissue and these responses were non-compentively antagonized with atropin. In Ca2+-five medium. acetylcholine and carhachol-induced contractions were 23.76±3.17 % and 16.27±3.93 % of the control responses, respectively and the responses to both agonists were increased hy re-addition of cumulative consentrations of Ca2+. The increased responses obtained with Ca2+ re-addition were inhihited with verapamil (10-8-10-6M) in a dose-dependent matıner. In serotonin pre-contracted tissues, cumulative addition of acetylcholine caused the inerease in serotonin responses. This augmenwd responses was found to be as 1 8.57±1 .72 % of initial serotonin conn-action. Pre-incubatiotı with L-NAME significantly augmented this additional contractions. In the tissue that contractility hy KCl was detected acetylcholine-induced contraction was 39.95±10.61 % of the KO responses. in spite of this hy the addition of L-NAME to the medium before acetylcholine-addition, this rano was 3226±10,7 %. The decreasing of the cont•actile responses was insignıficant (p>0.05). The results suggest that the contractions with acetylcholine and carhachol were dose-dependent and reproducibk and antagonized iri a non-competitive rnanner hy atropin and both extı-a- and intracellulaı-Ca2+ had a role in agoııists-induced responses In the resting ten.s-ion, the acervIcholine-induced contractions weı-e not diet-red hv L-NAME.