Plasma nociceptin/orphanin FQ levels rise after spontaneous episodes of angina, but not during induced myocardial ischemia

The aim of our study was to evaluate the effects of repeated episodes of angina and induced myocardial ischemia on plasma nociceptin/orphanin FQ (N/OFQ) levels. Patients with unstable angina (23 with new onset severe angina or accelerated angina and 18 with subacute angina at rest) who had had repeated spontaneous episodes of chest pain in the last week before the study underwent myocardial perfusion single-photon emission computed tomography using adenosine infusion. Twenty subjects without clinical symptoms of angina matched for age, sex and cardiac risk factors served as a control group. N/OFQ levels were significantly (P<0.01) higher in the patients (15.2+/-2.1 pg/ml) than in the control group (8.5+/-2.6 pg/ml). Blood pressure and heart rate did not significantly differ. All patients showed transient adenosine infusion myocardial ischemia that did not induce chest pain or significantly modify plasma N/OFQ levels or hemodynamic parameters. Our findings show that unstable angina is associated with a significant increase in circulating N/OFQ levels unrelated to intervening transient myocardial ischemia or hemodynamic changes. This increase is probably related to the chest pain repeatedly occurring in the course of coronary artery disease, but absent during transient adenosine-induced myocardial ischemia.