Effects of α₁-adrenoceptor blocker prazosin on microcirculation in terminal rabbit ileum

The influence of the specific α₁-blocker prazosin on the microcirculation of the terminal ileum was examined in 10 rabbits. For this purpose an isotope clearance test was carried out by administering ¹³³-Xenon solution into the intestinal wall before and after the intra-arterial injection of prazosin (1.0 mg) via the superior mesenteric artery. These experiments were supplemented by haemodynamic and thermographic measurements in a further group of 5 rabbits. Due to the systemic circulatory effect of prazosin, i.e. the drug-induced hypotension, the bowel segment exhibited, contrary to expections, significantly delayed values for isotope elimination indicating a reduced local tissue clearance and blood supply. Thermographic observations also confirmed the impairment of mesenteric blood flow after prazosin. Therapeutic applicability of α₁-adrenoceptor blockers to treat intestinal circulatory disturbances in diseases of vascular genesis thus remains dubious.