Abstract
The aim of this work was to observe any modulation of noradrenaline responses with nitric oxide (NO) in isolated Langendorff perfused rat hearts. The hearts were allowed to equilibrate for 1 h before the start of experiment. Then noradrenaline was added cumulatively in increasing concentrations from 10(-7) to 10(-2) M until a maximum inotropic and chronotropic responses occurred and further rises in the concentration did not produce any more increases in response. The same responses to noradrenaline occurred after administration of L-arginine, 10 mM (a nitric oxide donor). The positive chronotropic and inotropic responses of noradrenaline were significantly lower after L-arginine treatment (P < 0.05). These findings suggest that the nitric oxide attenuates the noradrenergic responses of the isolated heart. Med Sci Res 26:831-833. (C) 1998 Lippincott Williams & Wilkins.