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Glucocorticoid regulation of neuropeptide mRNAs in the rat striatum
1Rockefeller University, Laboratory of Neuroendocrinology, New York, NY 10021.
Abstract:
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.
Insights
Glucocorticoids regulate preprotachykinin (PPT) mRNA in rat striatum, increasing levels after 16 hours of corticosterone replacement in adrenalectomized rats. Preproenkephalin (PPE) mRNA shows diurnal variation, decreased by adrenalectomy but retaining rhythm.
Area of Science:
- Neuroscience
- Molecular Biology
- Endocrinology
Background:
- The striatum is a key brain region involved in motor control, reward, and habit formation.
- Glucocorticoids, stress hormones, are known to influence brain function and gene expression.
- Preprotachykinin (PPT) and preproenkephalin (PPE) are neuropeptide precursors expressed in the striatum.
Purpose of the Study:
- To investigate the regulation of PPT and PPE mRNA expression in the rat striatum by glucocorticoids.
- To determine the time course of corticosterone's effect on striatal PPT mRNA.
- To examine the influence of adrenalectomy and corticosterone on diurnal variations in PPE and PPT mRNA.
Main Methods:
- In situ hybridization was used to quantify PPT and PPE mRNA levels in rat striatal tissue.
- Experiments involved adrenalectomized (ADX) rats with and without corticosterone replacement.
- Time-course studies assessed mRNA levels after 2 and 16 hours of corticosterone treatment.
Main Results:
- Adrenalectomy decreased both PPT and PPE mRNA levels in the striatum.
- Corticosterone replacement in ADX rats increased PPT mRNA levels, with the effect evident after 16 hours but not 2 hours.
- Intact rats showed diurnal variation in PPE mRNA, which persisted after adrenalectomy.
- PPT mRNA did not exhibit significant diurnal changes in either intact or ADX rats.
Conclusions:
- Glucocorticoids play a significant role in regulating PPT mRNA expression in the rat striatum.
- The effect of corticosterone on striatal PPT mRNA is time-dependent.
- While adrenalectomy affects PPE mRNA levels and diurnal variation, PPT mRNA regulation by glucocorticoids appears distinct.
