Galanin message-associated Peptide-like immunoreactivity in the nervous system of the blowfly: distribution and...

Galanin message-associated peptide (GMAP) is a flanking peptide in mammalian preprogalanin located C-terminally of galanin (GAL). GMAP-like immunoreactive (LI) material in the brain of the blowfly Phormia terraenovae was analysed by radioimmunoassay combined with reversed-phase high-performance liquid chromatography and immunocytochemistry and compared to GAL-LI material. A sensitive radioimmunoassay, developed against a species-conserved portion of mammalian GMAP (synthetic porcine GMAP(19-41)amide), was applied to serially diluted blowfly head extracts. High-performance liquid chromatography combined with radioimmunoassay showed that the GMAP-LI material eluted as several different components with one major component coeluting with the synthetic GMAP fragment. One GMAP-LI peak co-eluted with a GAL-LI component of the extract. By immunocytochemistry it was shown that a distinct set of GMAP-LI neurons and neurosecretory cells is present in the blowfly brain and thoracico-abdominal ganglion. About 150 GMAP-LI cell bodies were found in the brain, distributed in the protocerebrum, tritocerebrum and suboesophageal ganglion. Several hundred GMAP-LI cell bodies were detected in the medulla of the optic lobe. In the fused thoracico-abdominal ganglion there are about 70 GMAP-LI cell bodies distributed in a segmental fashion. Several of the GMAP-LI neurons also contain GAL-LI material whereas some do not. In addition, there are GAL-LI neurons that do not react with the GMAP antiserum. Some of the GMAP-LI interneurons and neurosecretory cells could be traced in detail enabling a resolution of putative sites of action of the peptide.