THE INHIBITION OF SEROTONIN EVOKED BOVINE CORONARY-ARTERY CONTRACTIONBY HALOTHANE, ISOFLURANE AND SEVOFLURANE IS ENDOTHELIUM-INDEPENDENT

The present study was designed to determine the direct effects of halo thane, isoflurane and sevoflurane on the bovine epicardial coronary ar tery as well as their mode of action. We chose serotonin as the vasoco nstrictor because it also causes endothelium-dependent relaxation of c oronary arteries. Isolated spiral strips of bovine epicardial coronary artery with and without endothelium were suspended for isotonic contr action recordings in Tyrode's solution. KCI (80.4 mM) solution induced maximal contraction, regarded as the reference value (100%). The musc le strips were then exposed to increasing concentrations of serotonin from 10(-8) to 10(-4)M in the presence and absence of 1.5 MAC halothan e, isoflurane or sevoflurane. All three drugs attenuated serotonin-evo ked contraction in the coronary artery strips both those strips with a nd with out endothelium (P<0.05-0.001). However, there were no signifi cant differences in the attenuation of serotonin-induced contraction o f the strips, both with and without endothelium, in each drug group. T he attenuation potency of halothane was more than that of isoflurane a nd sevoflurane. The results demonstrate that halothane, isoflurane and sevoflurane attenuate contractile responses evoked by serotonin in bo vine epicardial coronary artery both with and without endothelium.