Repeated administration of desmethylimipramine blocks the reserpine-induced increase in tyrosine hydroxylase mRNA in locus coeruleus neurons of the rat

The levels of tyrosine hydroxylase and galanin mRNA were measured by in situ hybridization histochemistry in the rat locus coeruleus after repeated (21 days) administration of desmethylimipramine (10 mg/kg/day), of reserpine (0.25 mg/kg/day), of coadministered desmethylimipramine and reserpine, or of vehicle. Reserpine administration resulted in increased levels of both tyrosine hydroxylase and galanin mRNAs in locus coeruleus neurons as compared to vehicle-treated controls. Administration of desmethylimipramine alone failed to alter either the tyrosine hydroxylase or galanin mRNA. However, coadministration of desmethylimipramine with reserpine blocked the elevation in tyrosine hydroxylase mRNA induced by reserpine alone.