[Noradrenaline release induced by electrical field stimulation during ischemia and reperfusion in rat hearts]

The effects of the electrical field stimulation (6 Hz 5 v 2ms) on noradrenaline (NA) release during cardiac ischemia and reperfusion were studied in isolated perfused rat hearts. Endogenous NA was measured by high pressure liquid chromatography. Reproducible release during two subsequent stimulations (S1, S2) in all preparations showed that electrical field stimulation is a sufficient method for inducing exocytotic NA release. Ischemic periods of 10 min reduced markedly NA overflow from rat hearts (S2/S1 = 0.34, P < 0.01), while during the subsequent reperfusion period this suppression was abolished. These results indicate that excessive accumulation of NA is prevented by the endogenous inhibitor during early ischemia, a protective mechanism in early myocardial ischemia.