Galanin/GMAP- and NPY-like immunoreactivities in locus coeruleus and noradrenergic nerve terminals in the hippocampal formation and cortex with notes on the galanin-R1 and -R2 receptors

Abstract

By using immunofluorescence methodology, extensive galanin (GAL) and GAL message-associated peptide (GMAP)-positive terminal networks were observed in the hippocampal formation. The majority of the GAL/GMAP fibers were dopamine beta-hydroxylase- (DBH) positive, that is, they were noradrenergic. This finding was established with GAL/GMAP-DBH double-staining and with 6-hydroxy-dopamine treatment, which totally abolished all fibers in which GAL/GMAP and DBH coexisted. Also, reserpine treatment caused a marked depletion of GAL. No evidence for GAL/GMAP coexistence with 5-hydroxytryptamine was obtained. In the ventral hippocampus, GAL/GMAP-, DBH-negative fibers were seen in the stratum oriens, the anterior stratum radiatum, along the granule cell layer and in the strata oriens and alveus. In the locus coeruleus (LC), around 80% of the GMAP-positive neurons contained neuropeptide tyrosine (NPY), and about 40% of the NPY-positive neurons expressed GMAP. GAL-R1 receptor mRNA was expressed in Barrington's nucleus (close to the LC), but was not detected in the hippocampal formation/dorsal cortical areas. GAL-R2 receptor 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 present in noradrenergic nerve terminals originating in the LC, which has a robust GAL/GMAP synthesis. The functional role of GAL may be related to noradrenaline, possibly by a presynaptic action. However, the presence of GAL in other systems and of GAL-R2 receptor mRNA in granule cells also indicates other targets.

Differential Role of Galanin Receptors in the Regulation of Depression-Like Behavior and Monoamine/Stress-Related Genes at the Cell Body Level

“…In this context, the neuropeptide galanin (Tatemoto et al, 1983) is of particular interest, since it coexists with NA in the locus coeruleus (LC) and with 5-HT in the dorsal raphe (DR) nucleus (Melander et al, 1986;Xu and Hökfelt, 1997;Xu et al, 1998b). Electrophysiological, behavioral, and neurochemical studies have shown that galanin exerts modulatory (mainly inhibitory) effects on both the noradrenergic and serotonergic systems (Seutin et al, 1989;Sevcik et al, 1993;Pieribone et al, 1995;Xu et al, 1998c;Razani et al, 2001;Kehr et al, 2002;see Ö gren et al, 2006).…”

Upregulation of Galanin Binding Sites and GalR1 mRNA Levels in the Mouse Locus Coeruleus Following Chronic Morphine Treatments and Precipitated Morphine Withdrawal

“…Even following a dramatic increase during withdrawal, GalR1 mRNA levels were low compared to tyrosine hydroxylase mRNA (data not shown). Other investigators have also reported GalR1 mRNA expression in the LC (Gustafson et al 1996), although a second study found no GalR1 mRNA in the LC but rather saw GalR1 expression in the neighboring Barrington's nucleus (Xu et al 1998). In the negative study, oligonucleotide probes were used to detect GalR1 message.…”

Modulatory Effects of Galanin in the Lateral Bed Nucleus of the Stria Terminalis on Behavioral and Neuroendocrine Responses to Acute Stress

“…Galanin innervation of BSTL may originate in part from ascending brainstem noradrenergic afferents. Galanin is extensively co-localized with norepinephrine in ascending afferents from the locus coeruleus to the limbic forebrain (Holets et al 1988; Melander et al 1986c,d;Sawchenko and Pfeiffer 1988;Xu et al 1998). However, the primary noradrenergic innervation of BST arises from the medullary A1 and A2 cell groups (Delfs et al 2000).…”