This study was designed to evaluate the effects of calcium and potassium channel blockers on local anesthetics-induced vascular relaxation of isolated rat thoracic aorta. In the presence of lidocaine and bupivacaine, the aortic rings previously
contracted with phenylephrine(10E-4M) were slightly contracted at the beginning of the administration of local anesthetics. But in the presence of tetracaine, aortic rings were not contracted at the beginnings.
Verapamil, diltiazem and nifedipine in concentration of 10E-9M to 10E-5M produced cumulative concentration-dependent vasorelaxation significantly in the aortic rings previously contracted with phenylephrine(10E-4M).
In the presence of lidocaine, bupivacaine and tetracaine, verapamil, diltiazem and nifedipine in concentration of 10E-9M to 10E-5M caused dose-dependent vasorelaxation in aortic rings significantly.
Tetraethylammonium HCI(TEA) in concentration of 10E-9M to 10E-5M did not produce dose-dependent vasorelaxation but slight contraction showed at the beginning of the administration. In the presence of lidocaine, bupivacaine, TEA in concentration
of
10E-9M to 10E-5M did not produce vasorelaxation remarkably. But in the presence of tetracaine, TEA in concentration of 10E-9M to 10E-5M produced cumulative concentration-dependent vasorelaxation significantly.
These findings suggest that local anesthetics, especially tetracaine, which interact with calcium and potassium channel bleckers, lead to blockade of the sodium and calcium channels as well as potassium channels.
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