NITRIC-OXIDE SYNTHASE-CONTAINING NERVE-FIBERS AND NEURONS IN THE GALL-BLADDER AND BILIARY PATHWAYS OF THE GUINEA-PIG

WE investigated the distribution pattern of nitric oxide (NO) synthesi zing nerve cell bodies and axons in the biliary system of the guinea-p ig using immunohistochemistry for nitric oxide synthase (NOS). Nerve f ibres staining for NOS were found to contact non-vascular smooth myocy tes and to course beneath the epithelium. No perivascular NOS fibres w ere observed. The innervation density varied in different parts of the biliary tree. The lower portion of the common bile duct was more rich ly innervated than the remaining parts of the duct system. NOS-contain ing neurones encompassed a subpopulation of intramural ganglion cells. Sympathetic neurones in the coeliac ganglion were not stained. It is suggested that intrinsic NOergic neurones are involved in inhibitory m otor control of the biliary musculature, including the sphincter of Od di.