Effects of opioids on vasoresponsiveness of porcine coronary artery.

Myocardial ischemia during surgery can be caused by coronary vasospasm. Neurohumoral mechanisms are involved in this phenomenon, and various substances have been suggested as possible causes, including acetylcholine, histamine, and norepinephrine. The responses of isolated porcine coronary arteries (from 117 pig hearts) with (E+) and without (E-) endothelium to these agents were investigated in the presence of fentanyl, sufentanil, and morphine. Fentanyl significantly shifted to the right, in a concentration-dependent fashion, the concentration-response curve to acetylcholine. This effect was not different between E+ and E- rings. Neither sufentanil nor morphine altered acetylcholine-induced contraction of porcine coronary arteries. Naloxone did not antagonize the suppressive effect of fentanyl on acetylcholine-induced contraction. The response of porcine coronary arteries to norepinephrine was decreased only at very high concentrations of fentanyl. Neither sufentanil nor morphine altered norepinephrine-induced contraction of porcine coronary arteries. Fentanyl, sufentanil, and morphine had no effect on histamine-induced contraction. We conclude that fentanyl antagonized acetylcholine-induced contraction of porcine coronary arteries. This effect of fentanyl seems to be caused by a direct effect on smooth muscle cells and is not opioid-receptor mediated.