ISSN 2149-2263 | E-ISSN 2149-2271
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Agmatine facilitates sympathetic neurotransmission in frog myocardium via an action on alfa 2-adrenergic receptors [Anatol J Cardiol]
Anatol J Cardiol. 2006; 6(1): 34-38

Agmatine facilitates sympathetic neurotransmission in frog myocardium via an action on alfa 2-adrenergic receptors

Öcal Berkan1, M.Kemal Yıldırım2, İhsan Bağcivan2, Şahin Yıldırım2, Bülent Saraç2, Kasım Doğan1, Yusuf Sarıoğlu2
1Department of Cardiothoracic Surgery Faculty of Medicine, Cumhuriyet University, Sivas, Turkey
2Department of Pharmacology Surgery Faculty of Medicine, Cumhuriyet University, Sivas, Turkey

Objective: In this study, the effect of agmatine was studied on sympathetic neurotransmission in the frog isolated ventricular strips. Methods: Ventricular strips were prepared from the heart of the pitched frog. Each strip was mounted vertically in an organ bath. Musc- le contractions were recorded isometrically by a force displacement transducer and displayed on a polygraph. Results: Concentration-response relationships to noradrenaline were obtained on contractility of frog ventricular strips evoked by elect- rical stimulation. The responses of noradrenaline were re-obtained in presence of agmatine (3X10-4 M). Agmatine was found to be inef- fective on contractile responses of noradrenaline in electrically driven ventricular strips of frog heart. Transient additional stimulations (TAS) induced contractions. The contractions induced by TAS were re-obtained in presence of agmatine, idazoxan + agmatine and yo- himbine + agmatine. Agmatine significantly increased the positive inotropic responses of TAS. The effect of agmatine on contractile res- ponses of TAS was not changed by idazoxan, indicating that imidazoline receptors have not functions in this response. The effect of ag- matine on the contractile responses to TAS was reversed by yohimbine, indicating involvement of α2 adrenoceptors in this response. Ag- matine did not change the contractile responses of ventricular strips to exogenous noradrenaline, indicating that agmatine does not af- fect postjunctional adrenoceptors. Conclusion: These results suggest that agmatine facilitates sympathetic neurotransmission in frog myocardium via an action on prejunc- tional α2 adrenergic receptors located on sympathetic nerve terminals.

Keywords: Agmatine, a2 adrenoceptors, idazoxan, yohimbine, frog myocardium, sympathetic nerve activity

Öcal Berkan, M.Kemal Yıldırım, İhsan Bağcivan, Şahin Yıldırım, Bülent Saraç, Kasım Doğan, Yusuf Sarıoğlu. Agmatine facilitates sympathetic neurotransmission in frog myocardium via an action on alfa 2-adrenergic receptors. Anatol J Cardiol. 2006; 6(1): 34-38
Manuscript Language: English


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