Dopaminergic regulation of three somatostatin mRNAs in goldfish brain.

Three distinct somatostatin cDNAs characterized previously from goldfish brain encode three preprosomatostatins (PSS), designated as PSS-I, PSS-II and PSS-III. In this study, dopaminergic regulation of PSS gene expression was examined by Northern blot analysis in the forebrain of goldfish. Intraperitoneal injection of the non-selective dopamine (DA) agonist, apomorphine, significantly decreased the levels of all three PSS mRNAs, indicating an inhibitory regulation of PSS gene expression by DA. The involvement of DA receptor subtypes in the regulation of PSS gene expression was examined using the D1 receptor agonist and antagonist drugs SKF 38393 and SCH 23390, and the D2 agonist and antagonist drugs LY 171555 and pimozide, respectively. The results provide evidence for inhibitory and/or stimulatory regulation of PSS gene expression by DA through both D1 and D2 receptors, which are dependent on the temporal pattern of dopamine input and reproductive stage of the fish. Demonstration of involvement of both DA D1 and D2 receptors in the dopaminergic regulation of goldfish brain PSS gene expression is a novel finding, distinct from the observations in mammalian models.