NEUROPEPTIDE-Y (NPY) IN THE ORBITAL ARTERIES OF THE RABBIT - IMMUNOCYTOCHEMISTRY AND VASOMOTOR ACTIVITY

The purpose of the present study was to investigate the presence and v ascular effects of neuropeptide Y in the rabbit orbital arteries. Neur opeptide Y-containing nerve fibers were demonstrated, using an indirec t immunofluorescence method with a neuropeptide Y antiserum raised in goat against porcine neuropeptide Y, Isometric responses in isolated c ircular segments of the orbital arteries were measured following appli cation of neuropeptide Y, different contracting agonists, and the neur opeptide Y blocker alpha-trinositol. A rich supply of neuropeptide Y-c ontaining nerve fibers was seen around the orbital arteries, Neuropept ide Y (10(-10)-10(-6) M) did not induce any contractions in resting ar terial segments. Noradrenaline and histamine evoked concentration depe ndent constrictions which were potentiated by neuropeptide Y (3x10(-7) M). This potentiation was completely blocked by alpha-trinositol (3x1 0(7) M), The contractile effects of endothelin-1, endothelin-3, prosta glandin F-2 alpha, and 5-hydroxytryptamine were not modified by neurop eptide Y.