GALANIN GMAP-LIKE AND NPY-LIKE IMMUNOREACTIVITIES IN LOCUS-COERULEUS AND NORADRENERGIC NERVE-TERMINALS IN THE HIPPOCAMPAL-FORMATION AND CORTEX WITH NOTES ON THE GALANIN-R1 AND GALANIN-R2 RECEPTORS/

By using immunofluorescence methodology, extensive galanin (GAL) and G AL message-associated peptide (GMAP)-positive terminal networks were o bserved in the hippocampal formation. The majority of the GAL/GMAP fib ers were dopamine beta-hydroxylase-(DBH) positive, that is, they were noradrenergic. This finding was established with GAL/GMAP-DBH double-s taining and with 6-hydroxy-dopamine treatment, which totally abolished all fibers in which GAL/GMAP and DBH coexisted. Also, reserpine treat ment caused a marked depletion of GAL. No evidence for GAL/GMAP coexis tence with 5-hydroxytryptamine was obtained. In the ventral hippocampu s, GAL/GMAP-, DBH-negative fibers were seen in the stratum oriens, the anterior stratum radiatum, along the granule cell layer and in the st rata oriens and alveus. In the locus coeruleus (LC), around 80% of the GMAP-positive neurons contained neuropeptide tyrosine (NPY), and abou t 40% of the NPY-positive neurons expressed GMAP. GAL-Ri receptor mRNA was expressed in Barrington's nucleus (close to the LC), but was not detected in the hippocampal formation/dorsal cortical areas. GAL-RE re ceptor mRNA was found in the granule cell layer in the dentate gyrus. The present results show that most, but not all, immunohistochemically detectable GAL/GMAP in the hippocampal formation/dorsal cortex is pre sent in noradrenergic nerve terminals originating in the LC, which has a robust GAL/GMAP synthesis. The functional role of GAL may be relate d to noradrenaline, possibly by a presynaptic action. However, the pre sence of GAL in other systems and of GAL-RE receptor mRNA in granule c ells also indicates other targets. (C) 1998 Wiley-Liss, Inc.