1P258 Inotropec effects of acetylchollne on ventricular myocardium from embryonic and hatched chick

• Published in: Journal of Pharmacological Sciences 2003, Vol.91 (suppl.1), p.152-152
• Main Authors: Hideaki Nouchi, Kazuma Matsuura, Hikaru Tanaka, Koki Shigenobu
• Format: Article
• Language: Japanese
• ISSN: 1347-8613

In mammalian ventricular myocardium, acetylcholine (ACh) generally shows negative inotropy only when the contractile force was elevated by stimulation of adenylate cyclase. In the present study inotropic effects of ACh and carbachol (CCh) were examined in isolated ventricular preparations from embryonic and hatched chicken hearts. ACh and CCh produced positive and negative inotropic responses. They were not accompanied by changes in action potential configration and insensitive to phentolamine, propranolol, cimetidine, suramine and hexamethonium. The positive inotropic response was observed both in the embryo and hatched chicken with micromolar concentrations of CCh. It was antagonized by pirenzepine (PZ), but not by gallamine which indicated the involvement of M1 receptor. The negative inotropic response to CCh alone was observed only in myocardia from hatched chicks with submicromolar concentrations of CCh. When applied in the presence of PZ, negative response to CCh was also observed in the embryo. Although the negative response was affected by atropine and PZ, the prcise mechanisms awaits further investigation. In conclusion, we found that ACh produces positive and negative inotropy in developing chick ventricular myocardium, which is different from mammalian ventricle.