[Distribution, structure and transmitter content of nerve elements affecting the function of Oddi's sphincter]

Nerve elements containing neuropeptides were observed by using different antisera and Avidin-Biotin-Peroxidase technique and the distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d), a marker for nitric oxide (NO) synthase were studied in the ampulla hepatopancreatica (sphincter of Oddi) in the cat. A large amount of NPY, VIP, Substance P, somatostatin immunoreactive nerve fibers were found in all layers. Some immunoreactive nerve cell bodies (NPY, VIP, SP), were also observed in the wall. The NADPH-d stained cell bodies could be distinguished according to their size and the number of processes into two neuronal subtypes: large neurons with many dendrites and smaller, round cells with one or two processes. 99% of the cell bodies showed pozitive reactions for NADPH-d. The nerve fibers with NADPH-d activity were found in all layers, chiefly in the muscle layers. According to the distribution of the nerve fibers and the relationship to the effector cells, it is suggested, that these neuropeptides might have an important role in the function, and the NO containing nerve fibers are responsible for the nonadrenergic and noncholinergic inhibitory function.