DISTRIBUTION AND CHROMATOGRAPHIC ANALYSIS OF GALANIN MESSAGE-ASSOCIATED PEPTIDE (GMAP)-LIKE IMMUNOREACTIVITY IN THE RAT

Galanin message-associated peptide (GMAP) constitutes the C-terminal p art of the precursor protein encoding also the biologically active neu ropeptide galanin (GAL). We have raised antisera against a species-con served portion of GMAP, and investigated the localization of GMAP-like immunoreactivity (-LI) in relation to that of GAL-LI in the rat centr al and peripheral nervous system using the indirect immunofluorescence technique. In the central nervous system, GMAP-immunoreactive (-IR) c ell bodies were observed in the hypothalamus, while GMAP-IR nerve fibe rs were demonstrated in the septum, hypothalamus, pens and spinal cord . In the posterior pituitary and in the connecting infundibular stalk, weakly fluorescent GMAP-IR nerve fibers were observed. GMAP-IR nerve fibers were also observed throughout the gastrointestinal tract, i.e., from the stomach down to the colon, and in all layers, except in the epithelium, of the wall. In general, the staining of consecutive tissu e sections suggested that GMAP-IR was co-distributed with that of GAL- IR. A sensitive radioimmunoassay (RIA) for characterization of GMAP-IR in the rat central and peripheral nervous system was also developed. Characterization of GMAP-LI in acid extracts of rat brain and small in testine, using reverse phase high pressure liquid chromatography (rpHP LC), revealed multiple GMAP-IR forms that co-eluted with a synthetic p orcine GMAP(19-41)-amide fragment, or were less or more polar than thi s fragment. The corresponding chromatographic analysis of GAL-LI revea led only one: major form corresponding to rat GAL. The immunohistochem ical data indicate that a GMAP-like peptide(s) probably is axonally tr ansported and may possibly have pre- and/or post-synaptic functions. T he nature of the multiple GMAP-IR components remains to be investigate d, but may tentatively represent differently processed and/or chemical ly modified forms of rat GMAP(1-60).