Effects of serotonin and histamine on proximal and distal coronary vasculature in dogs: comparison with alpha-adrenergic stimulation.

The effect of several vasoactive agents on epicardial conductance arteries and distal resistance arteries was studied in intact dogs using a special catheter system to infuse vasoactive mediators directly into the left anterior descending coronary artery of intact dogs. Serotonin produced significant epicardial vasoconstriction (42% cross-sectional area reduction, p less than 0.01), whereas histamine had no effect on proximal coronary arteries. Phenylephrine, an alpha-adrenergic agonist, produced an 11% reduction in cross-sectional area. Distal coronary vascular resistance (pressure/flow) changes were small for serotonin and phenylephrine, whereas histamine significantly dilated the peripheral vascular bed and caused flow measured by xenon-133 washout to increase from 30.4 +/- 4.0 to 72.4 +/- 12.6 ml/min . 100 g (p less than 0.05). These results show that vasoactive mediators can have different actions on coronary resistance and conductance vessels. Serotonin is a potent vasoconstrictor of epicardial coronary arteries but does not produce significant constriction of coronary resistance vessels.