['Neuropeptides are important in the regulation of vascular functions. The purpose of the present study was to investigate the distribution of perivascular nerve fibers containing neuropeptides and nitric oxide synthase (NOS) in the rat ophthalmic artery.', 'Neuropeptide- and NOS-containing nerve fibers in the rat ophthalmic artery were identified using immunocytochemistry following unilateral parasympathectomy (electrocoagulation of the sphenopalatine ganglion) and sympathectomy (superior cervical ganglionectomy). The contralateral artery was used as control.', 'Nerve fibers containing vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and NOS were abundant in the wall of the ophthalmic artery. Nerve fibers containing calcitonin gene-related peptide and substance P were scarcer. Following destruction of the sphenopalatine ganglion there was no discernible change in the density of VIP- and NPY-immunoreactive fibers, while the majority of the NOS-containing fibers disappeared. Following sympathectomy the NPY-containing nerve fibers were almost completely eliminated, whereas VIP- and NOS-containing fibers were unaffected.'] Do vasoactive intestinal peptide- and nitric oxide synthase-containing nerve fibers in the rat ophthalmic artery have different origins?