Galanin‐R1 and ‐R2 receptor mRNA expression during the development of rat brain suggests differential subtype involvement in synaptic transmission and plasticity

Abstract

The present study employed 35S-labelled oligonucleotides and in situ hybridization to examine the distribution in the developing rat brain of mRNA encoding two galanin receptor subtypes, i.e. Gal-R1 and Gal-R2. Gal-R1 and/or Gal-R2 mRNA was detected at embryonic day (E) 20 and from postnatal day (P) 0-70. Gal-R1 mRNA was highly expressed in olfactory regions, ventral hippocampal CA fields, dorsomedial thalamic areas and many hypothalamic nuclei at all ages studied. In adult brain, Gal-R2 mRNA was most abundant in the dentate gyrus, anterior and posterior hypothalamus, raphe and spinal trigeminal nuclei, and in the dorsal motor nucleus of the vagus. At P0-P7, Gal-R2 mRNA was more widely distributed and abundant than at other ages, with highest levels of expression detected throughout the neocortex and thalamus. Thus, Gal-R2 transcripts had a more restricted distribution than Gal-R1 and were differentially abundant at different ages, while the distribution and relative abundance of Gal-R1 mRNA did not alter substantially during postnatal development. In general, Gal-R1 and -R2 mRNAs were localized in regions previously shown to contain [125I]-galanin binding sites and galanin-positive terminals in adult brain. Galanin-immunostaining was assessed in postnatal brain to determine whether peptide innervation correlated with observed transient receptor expression, but was not particularly enriched in Gal-R2 mRNA-positive areas of P4 or P7 brain. These results, together with earlier findings [e.g. Burazin, T. C. D. & Gundlach, A. L. (1998) J. Neurochem., 71, 879-882], suggest that Gal-R1 receptors have a broad role in normal synaptic transmission, while Gal-R2 receptors, in addition to a similar role in particular pathways, may be involved in processes prominent during the establishment and maturation of synaptic connections in developing brain and during neural damage and repair in the mature nervous system.

Distribution and regulation of galanin receptor 1 messenger RNA in the forebrain of wild type and galanin-transgenic mice

“…In the mesencephalon, relatively little GALR1 mRNA has been reported in the rat, except in the superior colliculus, central gray, and (in some studies) the substantia nigra (Burazin et al, 2000;Parker et al, 1995). In contrast, in the mouse we found GALR1 mRNA to be widely distributed throughout the midbrain, suggesting a more important role for galanin in these regions of this species compared with the rat.…”

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

“…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). Moreover, in vivo galanin can modulate 5-HT 1A preand postsynaptic receptor functions in an antagonistic manner (see Fuxe et al, 1998;Misane et al, 1998; The action of galanin is mediated via three G proteincoupled receptors, GalR1-GalR3 (see Branchek et al, 2000), which are expressed in the LC, DR, and their projection areas (Xu et al, 1998b, c;O'Donnell et al, 1999;Burazin et al, 2000;Larm et al, 2003;Hawes and Picciotto, 2004;Hawes et al, 2005;Swanson et al, 2005). Among these receptors, GalR1 and GalR3 mainly activate G i/o types of G proteins mediating inhibitory actions of galanin (Habert-Ortoli et al, 1994;Burgevin et al, 1995;Parker et al, 1995;see Branchek et al, 2000).…”

Depression-like behavior in rat: Involvement of galanin receptor subtype 1 in the ventral periaqueductal gray

“…There are three galanin receptors, GALR1-GALR3, which all belong to the family of seven transmembrane-spanning, G protein-coupled receptors (26)(27)(28)(29). They are found in many areas of the rat brain, as first shown with autoradiographic ligand-binding methodology (30,31), and later with in situ hybridization (ISH)/quantitative real-time PCR (qPCR) (32)(33)(34)(35)(36). The galanin system has been associated with numerous physiological and pathophysiological functions (29), including depression-and anxiety-like behaviors.…”