Neuropeptide Y (NPY) in the orbital arteries of the rabbit

ABSTRACT The purpose of the present study was to investigate the presence and vascular effects of neuropeptide Y in the rabbit orbital arteries. Neuropeptide Y‐containing nerve fibers were demonstrated, using an indirect immunofluorescence method with a neuropeptide Y antiserum raised in goat against porcine neuropeptide Y. Isometric responses in isolated circular segments of the orbital arteries were measured following application of neuropeptide Y, different contracting agonists, and the neuropeptide Y blocker α‐trinositol. A rich supply of neuropeptide Y‐containing nerve fibers was seen around the orbital arteries. Neuropeptide Y (10‐10 ‐10‐6 M) did not induce any contractions in resting arterial segments. Noradrenaline and histamine evoked concentration dependent constrictions which were potentiated by neuropeptide Y (3 times 10‐7 M). This potentiation was completely blocked by α‐trinositol (3 times 107 M). The contractile effects of endothelin‐1, endo‐thelin‐3, prostaglandin F2α, and 5‐hydroxytryptamine were not modified by neuropeptide Y.