Galanin receptor 1 is expressed in a subpopulation of glutamatergic interneurons in the dorsal horn of the rat spinal cord

• Published in: Journal of comparative neurology (1911) Vol. 499; no. 3; pp. 391 - 403
• Main Authors: Landry, Marc, Bouali-Benazzouz, Rabia, André, Caroline, Shi, Tie Jun Sten, Léger, Claire, Nagy, Frédéric, Hökfelt, Tomas
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 20.11.2006
• Subjects: 7-transmembrane receptor; analgesia; Animals; antinociception; Excitatory Postsynaptic Potentials - physiology; excitatory transmitter; Galanin - metabolism; Glutamate Decarboxylase - metabolism; Glutamic Acid - metabolism; Immunohistochemistry; In Situ Hybridization; Interneurons - cytology; Interneurons - metabolism; Isoenzymes - metabolism; Male; Medicin och hälsovetenskap; Mice; Mice, Inbred C57BL; Mice, Knockout; Neural Inhibition - physiology; neuropeptide; Nociceptors - physiology; pain; Pain - metabolism; Pain - physiopathology; Posterior Horn Cells - cytology; Posterior Horn Cells - metabolism; Rats; Rats, Sprague-Dawley; Receptor, Galanin, Type 1 - genetics; Receptor, Galanin, Type 1 - metabolism; RNA, Messenger - analysis; RNA, Messenger - metabolism; Synaptic Transmission - physiology; Vesicular Glutamate Transport Protein 2 - genetics; Vesicular Glutamate Transport Protein 2 - metabolism
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.21109

The 29/30 amino acid neuropeptide galanin has been implicated in pain processing at the spinal level and local dorsal horn neurons expressing the Gal1 receptor may play a critical role. In order to determine the transmitter identity of these neurons, we used immunohistochemistry and antibodies against the Gal1 receptor and the three vesicular glutamate transporters (VGLUTs), as well as in situ hybridization, to explore a possible glutamatergic phenotype. Gal1 protein, which could not be demonstrated in Gal1 knockout mice, colocalized with VGLUT2 protein, but not with glutamate decarboxylase, in many nerve endings in lamina II. Moreover, Gal1 and VGLUT2 transcripts were often found in the same cell bodies in laminae I–IV. Gal1‐protein and galanin‐peptide showed an overlapping distribution but were not colocalized. Gal1 staining did not appear to be affected by dorsal rhizotomy. Taken together, these findings provide strong evidence that Gal1 is a heteroreceptor expressed on excitatory glutamatergic dorsal horn interneurons. Activation of such Gal1 receptors may thus decrease the inhibitory tone in the superficial dorsal horn, and possibly cause antinociception. J. Comp. Neurol. 499:391–403, 2006. © 2006 Wiley‐Liss, Inc.