Localization of bombesin-, neuropeptide Y-, enkephalin- and tyrosine hydroxylase-like immunoreactivities in rat coeliac-superior mesenteric ganglion.

The localization of bombesin- (BOMB) and enkephalin- (ENK) immunoreactive (IR) nerves was studied in rat coeliac-superior mesenteric ganglion complex in relation to neuropeptide Y (NPY)- and tyrosine hydroxylase (TH)-immunoreactive neurons with an immunofluorescence double-staining method. Very dense networks of BOMB-IR nerve terminals surrounded the majority of the principal ganglion cells, whether or not they were TH-IR. BOMB-IR nerves were specifically related to the non-NPY-IR neurons. Moderately dense networks of ENK-IR fibers were unevenly distributed among the ganglion cells. Majority of these neurons exhibited TH-IR and some of them also contained NPY-IR. In sections double stained with antibodies to ENK and BOMB some nerve fibers contained both peptides. The findings suggest that BOMB-IR nerves, which have been previously demonstrated to originate from gut, control the function of non-NPY-IR ganglion cells. ENK-IR nerves apparently control the adrenergic neurons which project to gut and also some NPY-IR vasomotoric neurons. The finding that ENK- and BOMB-IR coexist in some nerves suggests that some ENK-IR nerves may originate from gut, although the major part probably represents preganglionic fibers originating from spinal cord.