[Dependence of arterial pressure and cardiac output on initial (regulated) arterial tone during beta-adrenoreceptor stimulation in rats].

A significant decrease of arterial pressure in response to isoproterenol occurred in anaesthetised rats with the initial pressure 101-130 mm Hg. Elevation of the initial pressure up to 131-180 mm Hg led to a significant attenuation of the depressor effect. The correlation analysis revealed transformation of direct correlation into inverse one between the depressor responses to isoproterenol and the degree of elevation of the initial arterial tone, as well as lack of such a dependence in the cardiac output shifts.