Vascular reactivities of isolated and perfused human ciliary arteries

The vascular responses to 8 agents, norepinephrine (NE), phenylephrine (PHE), xylazine (XYL), tyramine (TYR), dopamine (DA), 5-hydroxytryptamine (5-HT), prostaglandin F2 alpha (PGF2 alpha) and KCl were examined in human posterior ciliary arteries (HPCAs) which were isolated and perfused with Tyrode's solution gassed with 95% O2 and 5% CO2 under a constant flow rate at 37 degrees C. The rank order for potency of vasoconstrictions was 5-HT greater than NE greater than PHE = PGF2 much greater than DA greater than TYR much greater than KCl. Responses to XYL were various but not significant. DA frequently induced a vasodilatation at smaller doses but a vasoconstriction at larger doses. Although their antagonists were not used in this study, it was suggested that 1) there are rich alpha-1 adrenoceptors and 5-HT receptors, 2) dopaminergic receptors exist in these arteries and 3) there are rich tyramine-sensitive catecholamine stores in nerve terminals.