Non-analgesic effects of opioids: cardiovascular effects of opioids and their receptor systems.

Opioid peptides and their G protein-coupled receptors (GPCRs) are important regulators within the cardiovascular system, implicated in modulation of electrophysiological function, heart rate, myocardial inotropy, vascular function, and cellular stress resistance. The opioid system is also involved in cardiovascular development, adaptation to injury and effects of advanced age. The significant roles of opioids are emphasized by the observation that the heart produces prodynorphin and proenkephalin, which are enzymatically processed from small to large active polypeptides. Indeed, depending on species, cardiac preproenkephalin mRNA levels are comparable to or higher than those found in the central nervous system. This review highlights and discusses current knowledge and recent findings regarding physiological and pathophysiological modulation of the heart and vessels by the opioid receptor system.