Immunohistochemical demonstration of galanin‐, and galanin message‐associated peptide‐like immunoreactivities in sympathetic ganglia and adrenal gland of the guinea pig

Abstract Using the indirect immunofluorescence method, the distribution of galanin (GAL)‐ and galanin message‐associated peptide (GMAP)‐like immunoreactivities (LI) were studied in sympathetic ganglia and the adrenal gland of the guinea pig. A rather dense network of GAL‐immunoreactive nerve fibers was found in the inferior mesenteric ganglion (IMG) and in the superior mesenteric pole of the celiac‐superior mesenteric ganglion complex (C‐SMG). The celiac pole of the C‐SMG, the stellate ganglion, and the superior cervical ganglion contained fewer, mostly scattered fibers. SIF‐cells in prevertebral and paravertebral ganglia contained GAL‐LI, as did the adrenal medullary cells. The GAL fibers in the IMG surrounded mainly principal ganglion cells containing somatostatin‐immunoreactivity (SOM‐IR), whereas fewer fibers were seen around neuropeptide Y (NPY) cells and cells in which SOM and NPY coexisted. Application of colchicine or vinblastine onto the IMG did not result in the appearance of GAL‐IR in the principal ganglion cells. In denervation experiments it was revealed that most of the GAL fibers reach the IMG via the lumbar splanchnic nerves. GAL‐IR appears to be colocalized with substance P (SP) in fibers of the IMG, indicating an origin of the GAL‐containing fibers in dorsal root ganglia (DRG). This conclusion was supported by the finding in lumbar DRGs of GAL‐positive cell bodies that contained SP. The role of GAL in prevertebral ganglia is unclear. It may be suggested that GAL modulates the slow, long‐lasting membrane depolarization of the principal ganglion cells caused by SP in the primary afferents related to the IMG. GMAP‐LI was detected in SIF cells and adrenal medullary cells in which GMAP‐LI parallels the immunoreactivity of GAL. GMAP‐LI was not observed in neuronal cell bodies or nerve fibers of the ganglia. © 1994 Wiley‐Liss, Inc.