Special Issue on Galanin Galanin in neuro(glio)genesis: expression of galanin and receptors by progenitor cells in vivo and in vitro and effects of galanin on neurosphere proliferation Pei-Juan Shen a , Chong-Gang Yuan b , Ji Ma b , Shuang Cheng b , May Yao c , Ann M. Turnley d , Andrew L. Gundlach a, * a Howard Florey Institute of Experimental Physiology and Medicine, The University of Melbourne, Vic. 3010, Australia b Faculty of Life Science, East China Normal University, Shanghai 200062, PR China c School of Human Biosciences, La Trobe University, Vic. 3086, Australia d Centre for Neuroscience, The University of Melbourne, Vic. 3010, Australia Received 10 December 2004; accepted 10 December 2004 Available online 28 January 2005 Abstract Considerable recent evidence suggests that in addition to its neuromodulatory role, galanin, like several other neuropeptides, also plays an important trophic role during development and after adult neural injury. Studies in our laboratory have identified high levels of galanin and galanin receptor expression in the subventricular zone, rostral migratory stream, subgranular zone of dentate gyrus and the medial corpus callosum – which include the main sites for continuing cell proliferation in both adult and developing rat brain. Galanin expression was also strongly and transiently induced in oligodendrocyte progenitor cells (OPCs) throughout the neocortex and corpus callosum by a benign physiological stimulus, cortical spreading depression (CSD). SD-like depolarization also occurs in peri-infarction areas following cerebral ischemia and is associated with proliferation of OPCs and transiently increased galanin expression. Together, these data suggest a putative role for galanin in regulating progenitor or Ôstem cellÕ proliferation, migration and/or differentiation. Cultured adult and embryonic stem cells or ÔneurospheresÕ express galanin and galanin receptor mRNA and preliminary studies suggest that sub-acute galanin treatment of cultured neurospheres decreases cell proliferation/sur- vival, possibly by effects on the rate of apoptosis via GalR2 receptors. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Galanin; GalR1-3 receptors; Neurogenesis; Oligodendrocyte progenitors; Proliferative zones; Spreading depression 1. Introduction – Galanin as a neuromodulator and trophic factor Galanin is widely expressed in the mammalian central nervous system. In rat brain, the 29 amino acid peptide co-exists with several classical neurotransmitters (Mel- ander et al., 1986) and has strong inhibitory actions on synaptic transmission by reducing the release of these neurotransmitters (Fisone et al., 1987; Pieribone et al., 1995). These inhibitory actions result in diverse physio- logical functions of galanin in nociception (Liu and Ho ¨kfelt, 2002), metabolism and reproduction (Crawley, 1999; Gundlach, 2002) and cognition (Wrenn et al., 2004). Galanin is also thought to play a role in patho- logical conditions, such as AlzheimerÕs disease (Counts et al., 2001; Jhamandas et al., 2002) and epilepsy (Ko- kaia et al., 2001; Mazarati et al., 2000). 0143-4179/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.npep.2004.12.021 * Corresponding author. Tel.: +61 3 8344 7324; fax: +61 3 9348 1707. E-mail address: a.gundlach@hfi.unimelb.edu.au (A.L. Gundlach). www.elsevier.com/locate/npep Neuropeptides 39 (2005) 201–205 Neuropeptides