OPIOID RECEPTORS AND MYOCARDIAL PROTECTION - DO OPIOID AGONISTS POSSESS CARDIOPROTECTIVE EFFECTS

In an in vivo rat model of myocardial infarction, opioid receptor stim ulation has been observed to result in a reduction in infarct size sim ilar to that produced by ischaemic preconditioning. The ability of gli benclamide to abolish this effect suggests an involvement of the myoca rdial ATP-sensitive potassium (K-ATP) channel. Importantly, it has rec ently been demonstrated that glibenclamide can completely abolish the protective effects of preconditioning in humans, suggesting that K-ATP channel opening may be an endogenous protective mechanism in humans. In this article we report recent findings that indicate that opening o f the K-ATP channel is differentially involved in the antinociceptive effect of some opioids, including buprenorphine, morphine and methadon e, but not that of others such as fentanyl or levorphanol. We argue th at these findings may also be relevant to the effects of opioids in pe ripheral tissue, such as the myocardium, and that they may have import ant clinical ramifications. On the basis of our analysis and interpret ation of these in vivo data, we speculate that some opioid agonists, n otably buprenorphine, may possess previously unrecognised beneficial c ardioprotective effects in some groups of patients, including those un dergoing coronary artery bypass and those experiencing an acute myocar dial infarction.