Acute systemic and regional hemodynamic effects of alpha 1-adrenoceptor blockade in conscious spontaneously hypertensive rats.

The acute hemodynamic effect of the selective alpha1-antagonist, 2-[4-(n-butyryl)-homopiperazine-1-y1]-4-amino-6,7-dimethoxy-quinazoline (bunazosin; E-643), was studied by the microsphere technique in 62 conscious spontaneously hypertensive rats. We found that a large fall in total peripheral resistance with a moderate increase in cardiac output accounted for the moderate decrease in arterial pressure; the heart rate did not change; the skeletal muscle, brain, heart, and gastrointestinal tract sensitively dilated, and kidney less sensitively dilated, their resistance vessels, with little change in their blood flow.