The antidepressant-like effect of galanin in the dorsal raphe nucleus of rats involves GAL2 receptors

Galanin is a neuropeptide distributed in human and rat brain regions that are involved with emotional regulation, such as the dorsal raphe nucleus (DRN). Galanin effects in the DRN are mediated by GAL(1) and GAL(2) receptors. Intracerebral infusion of a GAL(2) (AR-M1896) or a GAL(1) (M617) agonist induced either antidepressant or depressive-like effect, respectively, in rats exposed to the forced swimming test (FST). However, it is not clear if GAL(1) and/or GAL(2) receptors present in the DRN would be involved in such effects. Therefore, we investigated the effects induced by intra-DRN infusion of galanin (0.3 nmol), AR-M1896 (1 nmol, GAL(2) agonist), or M617 (GAL(1) agonist) in rats exposed to the FST. Galanin and AR-M1896 intra-DRN administration induced anti-depressant-like effect in the FST. However, M617 did not induce any change in the FST. Neither M617 nor AR-M1896 changed the locomotor activity of rats in the open field test. Intra-DRN pre-treatment with M871 (1 nmol), a selective GAL(2) antagonist, counteracted the antidepressant-like effect induced by galanin. These results suggest that galanin signaling through GAL(2) receptors in the DRN produces triggers antidepressant-like effect.