COMPARISON OF THE NPY RECEPTORS MEDIATING VASOCONSTRICTION OF THE GUINEA-PIG UTERINE ARTERY AND THORACIC VENA-CAVA USING A RANGE OF NPY ANALOGS

The ability of analogues of neuropeptide Y (NPY) to produce direct vas oconstriction, or to antagonize NPY constrictions, was examined in iso lated segments of the thoracic vena cava and the uterine artery of gui nea-pigs, where NPY mediates a slow phase of sympathetic vasoconstrict ion. [Leu31,Pro34]NPY, NPY(13-36) and NPY(18-36) all contracted the ut erine artery and the vena cava. Contractions produced by [Leu31,Pro34] NPY were similar in time course to those produced by porcine NPY (pNPY ), although contractions produced by NPY(13-36) or NPY(18-36) typicall y were slower than pNPY contractions. In both vessels the order of pot ency of the agonists was pNPY greater-than-or-equal-to [Leu31,Pro34]NP Y > NPY(13-36) > NPY(18-36). High concentrations (10(-5) mol.l-1) of p NPY or [Leu31,Pro34]NPY produced desensitization of contractions of th e uterine artery produced by NPY(13-36). The reported NPY receptor ant agonists, PYX-1 and PYX-2 (5 x 10(-6) mol.l-1), slightly reduced (by 2 1-47%) the magnitude of constrictions produced by exogenous pNPY (1-3 x 10(-8) mol.l-1) in both the uterine artery and the vena cava. These results show that the NPY receptors mediating slow sympathetic vasocon striction of both the uterine artery and the vena cava are likely to b e predominantly Y1 receptors, despite differences between the adrenoce ptors mediating sympathetic responses in the two blood vessels.