Alpha-adrenoceptors in the vessels of human finger skin

To characterize alpha-adrenoceptors in the blood vessels of finger skin the effects of selective alpha-1 and alpha-2 adrenoceptor agonists and antagonists on skin blood flow were studied in vivo. The vasoactive substances were administered into the skin by iontophoresis and the effects on blood flow were evaluated with a laser-doppler. After blockade of alpha-1 adrenoceptors with doxazosine, the blood flow reduction induced by the alpha-1 selective agonist, phenylephrine, was diminished but not that caused by the alpha-2 selective agonist, B-HT 933. In contrast, after alpha-2 selective blockade by rauwolscine, phenylephrine but not B-HT 933 caused a marked decrease in blood flow. The results are compatible with the concept that postjunctional alpha-adrenoceptors in human finger skin vessels are of both alpha-1 and alpha-2 subtypes.