Acute systemic and regional haemodynamic profile of prazosin in conscious hypertensive rabbits.
We used the radioactive microsphere technique to study the acute systemic and regional haemodynamic effects of prazosin (0.01, 0.03 and 0.10 mg/kg i.v.) in conscious hypertensive rabbits. The alpha 1-adrenoceptor antagonist decreased arterial blood pressure dose dependently and increased the heart rate. There was a reduction in stroke volume which resulted in a significant fall in cardiac output at the highest dose of prazosin. Due to the prazosin-induced vasodilatation in the kidneys, intestines and bones, the blood flow to these tissues was not reduced despite the decrease in cardiac output. In contrast, a reduction in the blood flow to the skeletal muscles, skin and, at the highest dose, to the heart, brain and stomach followed prazosin administration. In conclusion, the selective vasodilatation produced by prazosin causes a redistribution of the cardiac output at the expense of vital organs such as the brain, and this finding may possibly explain the symptoms related to the "first dose phenomenon" of prazosin in man.
D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008863:Microspheres; D011224:Prazosin / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology*; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects; D012079:Renal Circulation / Q000187:drug effects
D011799:Quinazolines; D011224:Prazosin