| The galaninergic system, comprised of galanin and galanin-like peptide (GALP) and its receptors (GalR1, GalR2, GalR3), is involved in diverse physiological functions. In this study partial cDNAs encoding zebrafish preprogalanin 2B and GaIR2, and goldfish GalR1-L and GalR2 were identified and found widely expressed in various tissues of both species. GalR1 and GalR2-like immunoreactivities were detected in the goldfish brain and the gut, while GALP-like immunoreactivity was found in the brain. Periprandial studies in goldfish showed subtype-specific changes in receptor mRNA levels but no fasting-induced changes. Galanin inhibited spontaneous goldfish gut contractions while increasing the force of acetylcholine-induced contractions. Intracerebroventricular injections of GALP in goldfish caused an increase in food intake and in GalR1-L and GaIR2 hypothalamic mRNA expression. Together, these results provide support for the role of the galaninergic system in the maintenance of energy homeostasis in fish. |
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