Glucocorticoid regulation of neuropeptide mRNAs in the rat striatum.

Expression of the preprotachykinin (PPT) mRNA and of the preproenkephalin (PPE) mRNA in the rat striatum has been assessed by in situ hybridization. The results demonstrate that the PPT mRNA is regulated by glucocorticoids such that adrenalectomized (ADX) animals replaced with corticosterone for 5 days expressed higher levels of the mRNA than ADX animals. The corticosterone-induced increase in striatal PPT mRNA was evident after 16 h, but not after 2 h, of corticosterone treatment of ADX animals. Elevation of circulating corticosterone levels in intact rats by acute restraint stress, or by corticosterone injection did not change the level of PPT mRNA in the striatum. In intact rats there was a diurnal variation in the level of striatal PPE mRNA expression; adrenalectomy resulted in a decrease in the mRNA level and did not abolish the diurnal variation in expression. The level of PPT mRNA in the striatum was also decreased in response to ADX, but there were no significant diurnal changes in the expression of the PPT mRNA either in the intact or in the ADX animals.