Elsevier

Neuroscience

Volume 158, Issue 2, 23 January 2009, Pages 537-544
Neuroscience

Cellular Neuroscience
Dopamine receptor-mediated regulation of neuronal “clock” gene expression

https://doi.org/10.1016/j.neuroscience.2008.10.044Get rights and content

Abstract

Using a transgenic mice model (i.e. “clock” knockouts), clock transcription factors have been suggested as critical regulators of dopaminergic behaviors induced by drugs of abuse. Moreover, it has been shown that systemic administration of psychostimulants, such as cocaine and methamphetamine regulates the striatal expression of clock genes. However, it is not known whether dopamine receptors mediate these regulatory effects of psychostimulants at the cellular level. Primary striatal neurons in culture express dopamine receptors as well as clock genes and have been successfully used in studying dopamine receptor functioning. Therefore, we investigated the role of dopamine receptors on neuronal clock gene expression in this model using specific receptor agonists. We found an inhibitory effect on the expression of mClock and mPer1 genes with the D2-class (i.e. D2/D3) receptor agonist quinpirole. We also found a generalized stimulatory effect on the expression of clock genes mPer1, mClock, mNPAS2 (neuronal PAS domain protein 2), and mBmal1 with the D1-class (i.e. D1) receptor agonist SKF38393. Further, we tested whether systemic administration of dopamine receptor agonists causes similar changes in striatal clock gene expression in vivo. We found quinpirole-induced alterations in mPER1 protein levels in the mouse striatum (i.e. rhythm shift). Collectively, our results indicate that the dopamine receptor system may mediate psychostimulant-induced changes in clock gene expression. Using striatal neurons in culture as a model, further research is needed to better understand how dopamine signaling modulates the expression dynamics of clock genes (i.e. intracellular signaling pathways) and thereby influences neuronal gene expression, neuronal transmission, and brain functioning.

Section snippets

Preparation of primary cultures of striatal neurons and drug treatments

For the preparation of primary neuronal cultures from the striatum, we used ICR mice (Harlan, Indianapolis, IN, USA). Mice were housed in a temperature-controlled room under conditions of a 14-h light/10-h dark cycle (lights on at 5 am). The experimental protocols were approved by the Institutional Animal Care and Ethics Committee of the University of Illinois at Chicago. All experiments were performed under these approved experimental protocols and the number of the subjects kept controlled by

Results

DA receptors and clock genes are expressed in striatal neurons in culture (Fig. 1). Gene specific primer pairs (see Table 1 for primer sequences) detected the expected size PCR products in gel electrophoresis for D1 (404 bp), D2 (532 bp), and D3 (536 bp) DA receptors and the clock genes, mPer1 (387 bp), mClock (534 bp), mBmal1 (471 bp), and mNPAS2 (458 bp) (Fig. 1). Moreover, mCLOCK and D2 DA receptor proteins co-exist in the same neurons in culture (Fig. 1). Since co-labeling studies revealed

Discussion

In this study using DA receptor specific drugs (i.e. agonists), we demonstrated that DA receptor-mediated intracellular signaling differentially regulates neuronal clock gene expression at the cellular level (i.e. striatal neurons in culture). Further, we found that when given systemically, the DA receptor agonist quinpirole regulates the striatal expression of the clock gene mPer1 depending on the time of injection.

As a part of the mesolimbic system, the striatum is primarily involved in the

Conclusion

In conclusion, using a neuronal culture model (i.e. primary striatal cultures) in vitro as well as a protracted DA receptor-specific drug treatment protocol in vivo, we have demonstrated that DA receptors mediate neuronal clock gene expression. Our results clarify at least in part the underlying mechanisms of the regulatory role of the psychostimulant/DA system on clock gene expression dynamics. Future studies using neuronal culture models are needed to understand the underlying mechanisms of

Acknowledgments

We acknowledge support from the Psychiatric Institute, UIC and by NIH grants R01 DA15072 (T.U.), R01 MH61572 (H.M.), and K01 MH069839 (R.S.).

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