Galanin expression is decreased by cAMP-elevating agents in cultured sympathetic ganglia

GALANIN expression is co-regulated in peripheral neurons with that of vasoa ctive intestinal peptide (VIP) under a variety of conditions. For example, the expression of both increase after explantation of adult rat superior ce rvical ganglia (SCG). Because VIP participates in a positive feedback loop regulating its own expression, we examined whether VIP also increases galan in expression. Galanin mRNA and peptide are nearly undetectable in the SCG in vivo, but increase dramatically after 24-48 h in organ culture. Addition off VIP or forskolin to the culture medium reduced galanin mRNA expression by 75% and 77%, respectively, and reduced galanin peptide expression by 76 % and 82%, respectively, compared with ganglia cultured in control medium. In contrast, isoproterenol stimulation did not significantly alter levels o f galanin mRNA or peptide, consistent with previous observations that isopr oterenol exerts its effect on SCG non-neuronal cells, but not on neurons. T he results indicate that galanin and VIP are differentially regulated in sy mpathetic neurons by cAMP- elevating agents. (C) 1999 Lippincott Williams & Wilkins.