Behavioral actions of galanin and galanin fragments

Abstract

The anatomical distribution of galanin in mammalian brain suggests important behavioral functions of this twenty-nine amino acid neuropeptide. Galanin-like immunoreactivity coexists with choline acetyl-transferase-1ike immunoreactivity in cholinergic basal forebrain neurons innervating the hippocampus of rats, and the hippocampus and cerebral cortex of rats and primates (Melander et al., 1986a,b; Chan-Palay, 1988; Walker et al., 1989; Kordower and Mufson, 1990). Localization of galanin in the cholinergic septohippocampal pathway suggests that galanin may play a role in learning and memory processes. Localization of galanin in 80–90% of the noradrenergic neurons of the locus coeruleus (Melander et al., 1986a; Holets et al., 1988), and in a smaller percentage of serotonergic raphe neurons (Melander et al., 1986a), indicates a possible role for this peptide in arousal and stress responses, which may be relevant to clinical depression. Localized in the dorsal horn of the spinal cord (Ch’ng et al., 1985; Melander et al., 1986a) and coexisting with cholecystokinin in the spinothalamic tract (Ju et al., 1987; Blasco et al., 1989), galanin could contribute to pain transmission and analgesia. The paraventricular nucleus of the hypothalamus, which mediates feeding behaviors, contains high concentrations of galanin (Melander et al., 1986a; Skofitsch and Jacobowitz, 1986; Palkovits et al., 1987; Sawchenko and Pfeiffer, 1988; Bonnefond et al., 1990), and receives terminals from the locus coeruleus neurons in which galanin and norepinephrine coexist (Levin et al., 1987; Holets et al., 1988).