Galanin and Kindling.

Galanin is a 29 aminoacid residue neuropeptide (30 amionoacids in humans) widely distributed throughout central nervous system and intestines1,2 that has been shown to be involved in regulation of numerous processes; such as feeding, nociception, nerve regeneration, memory, neuroendocrine release, intestine secretion and contractility (see 2). In the brain, galanin is normally present in cholinergic and noradrenergic neuronal populations of the medial septum and locus coeruleus, respectively.3-10 It is transported and subsequently released by the extensive axonal projections of these neurons into a wide range of forebrain regions, including the hippocampus. In addition, intrahippocampal colchicine administration, which blocks fast axonal transport and mitosis, produces scattered galanin-immunoreactive neurons and glial cell bodies in the hippocampus.2,11 Galanin acts via 3, so far identified, distinct G-protein-linked receptor subtypes: GalR1, GalR2 and GalR3.12-16 Similar to galanin, GalR1 and GalR2 (but not GalR3) mRNAs are abundantly expressed in many brain areas.17,18 The detailed mapping of galanin mRNA, its immunoreactivity and binding sites demonstrated that for the most part mRNA expression matches with observed immunoreactivity in the cells, and that receptor binding sites correlate well with galanin-immunoreactive fiber bundles in various regions of the rat brain (for details see2). Activation of GalR1 and GalR3 has been shown to inhibit adenylyl cyclase, decrease cAMP concentration, and open G-protein-coupled inwardly rectifying K+ channels. GalR2 stimulates phospholypase C and PKC action.13,19,20 [ABSTRACT FROM AUTHOR]