Tissue blood flow in the left ventricle of open chest dogs was registered with the aid of the heat clearance technique. Coronary sinus outflow was measured simultaneously as an index of overall coronary flow. In the control state supramaximal stimulation of the stellate ganglion as well as intravenous infusion of noradrenaline (0.1-4.0 μg/kg/min) elicited a considerable increase both in the myocardial tissue flow and in the sinus outflow. The degree of coronary dilatation registered in the coronary sinus was, however, significantly greater than that of the augmentation in the tissue blood flow. When pure alpha adrenergic activity was unmasked by blockade with propranolol (0.2-0.4 mg/kg), a different relationship was observed between these two flow parameters. After beta blockade sympathetic excitation brought about coronary constriction in the overall flow. On the other hand, alpha adrenergic activation did not induce a comparable flow decrease in the myocardial tissue. Instead of declining, myocardial heat clearance often increased considerably on pure alpha adrenergic activation. The results suggest that excitation of the coronary constrictor fibres creates favourable conditions for an improved distribution of the myocardial blood supply at the capillary level.
|Number of pages||12|
|Journal||Archives internationales de pharmacodynamie et de therapie|
|Publication status||Published - Dec 1 1973|
ASJC Scopus subject areas