Methods: The thoracic aorta segments collected from 30 male Wistar rats (20 endothelialized and 20 de-endothelialized vascular rings for each drug in 2 mm wide strips, total number of 120 vascular rings) were suspended into the Krebs solution of the isolated tissue bath system. Phenylephrine was used to induce isometric contraction and tissue samples were treated with verapamil, papaverine and nitroglycerin separately to draw concentration-response curves of isometric vasodilatory responses. This procedure was repeated for de-endothelialized aorta samples.

Results: Papaverine and verapamil induced vasodilatatory responses starting from the concentration of 10^-8 M and reached its maximum at concentration of 10^-3 M, while nitroglycerin induced vasodilation at lower concentrations starting from a concentration of 10^-12 M, reaching its maximum at 10^-6 M. Nitroglycerin was the most potent agent, followed by verapamil and papaverine. Efficacy analysis revealed that the most efficient agents were papaverine (140±6.7%), nitroglycerin (110.8±1.35%) and verapamil (99±4.14%), respectively. The results were similar in aorta samples without endothelium (p≥0.05, F test).

Conclusion: In this study examining isolated rat aorta, nitroglycerin was the most potent agent, while papaverine was the most efficient agent. Our study results showed that endothelium played no role in vasodilatation responses of these drugs.