[Dissociation of the ino- and chronotropic response of isolated rat heart to noradrenaline in the presence of oxygen deficit, exposure to cyanide and 2,4-dinitrophenol].

Isolated hearts of rats responded to increasing doses of noradrenaline (NA) with progressing increase of the sistolic pressure in the left ventricle and with bradycardia. Tachyrhythmic response occurred only at high concentration of NA (5-10(-8)). During energy hunger induced by O2 deficit, cyanide, and 2,4-dinitrophenole the NA inotropic effect has reduced, but the relative stabilization of the heart integral response (Opil's index) was achieved due to activation of NA positive chronotropic effect. The character of NA effects under conditions of energy hunger does not depend on the initial level of endogenous NA. Even in the isolated heart at ATPh deficit a compensatory mechanism comes to action switching the NA regulating effect from the contractile process over to activation of pacemaker rhythmic activity.