Efectos Vasculares del Tiopental

Effects of thiopental on rat aortic rings were investigated. The anesthetic produced contraction which was higher when the endothelium was removed. The absence of calcium but not the presence of indomethacin (10^-5 M), prazosin (10^-6 M), idazoxan(10^-6 M) or diltiazem(10^-6 M) decreased thiopental's contractile effect. On the other hand, thiopental relaxed in an endothelium-independent fashion, aortic rings precontracted with phenylephrine (10^-6 M), angiotensin (10^-7 M), serotonin (3.1 x 10^-5 M) or KCl (40 mM). Finally the exposure to thiopental(3.1 mg/ml) reversibly inhibited relaxation elicited by histamine but no by sodium nitroprusside or A23187. In conclusion, in rat aorta thiopental elicited: a) contraction inhibitory modulated by the endothelium which is not mediated by prostaglandins or adrenoceptors but it is dependent of extracelular calcium moving through channels non sensitive to diltiazem; b) relaxation independent both of the endothelium and the contractile agent employed; and c) inhibition of the endothelium-dependent relaxation elicited by histamine. The latter effects does seem to be result of guanylate cyclase or nitric oxide synthase alterations since thiopental did not inhibit the effect of sodium nitroprusside or A23187. It is possible that the diverse vascular effects of thiopental are associated with its ability to be dissolved into the membrane of aortic smooth muscle and endothelial cells, disturbing their functional components.