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Modulation by chronic morphine administration of single-stranded cAMP response element (ssCRE) binding proteins in
1Department of Pharmacology I, Osaka University School of Medicine, Japan.
Abstract:
The development of opiate tolerance and dependence are thought to be associated with gene expression. Our previous studies have shown that the binding activity of nuclear factors to a single-stranded oligo-DNA containing cAMP response element (ssCRE) is altered by long term treatment with morphine in cultured neuronal cells. In the present experiments, the effects of acute and chronic treatments with morphine on the binding of nuclear proteins to single- and double-stranded oligo-DNAs of the cAMP response element were studied in the mouse brains by using gel shift assay. The activity of single-stranded CRE binding proteins (ssCRE-BP) was decreased by chronic morphine treatment to about 40% of control in the cerebellum. The effect of chronic morphine treatment on the binding activity persisted for at least 2 weeks after morphine withdrawal. The activity of double-stranded CRE binding proteins was also detected in the cerebellum, but it was insensitive to the morphine treatment. The activity of ssCRE-BP was also decreased by acute morphine treatment in 5 h, but it returned to control level in 24 h. These data suggest that the change of ssCRE-BP can be involved in the development of tolerance and dependence.
Insights
Chronic morphine treatment reduces single-stranded cAMP response element-binding proteins (ssCRE-BP) in mouse brains, a change that persists after withdrawal and may contribute to opiate tolerance and dependence.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Opiate tolerance and dependence are linked to gene expression changes.
- Previous studies indicated altered nuclear factor binding to single-stranded cAMP response elements (ssCRE) with chronic morphine in neuronal cells.
Purpose of the Study:
- To investigate the effects of acute and chronic morphine on nuclear protein binding to single- and double-stranded cAMP response elements (CRE) in mouse brains.
- To determine if changes in CRE binding proteins are associated with opiate tolerance and dependence.
Main Methods:
- Gel shift assay was used to study nuclear protein binding to oligo-DNAs in mouse brain tissue.
- Acute and chronic morphine treatments were administered to mice.
- Binding activity of single-stranded CRE binding proteins (ssCRE-BP) and double-stranded CRE binding proteins was measured.
Main Results:
- Chronic morphine treatment significantly decreased ssCRE-BP activity in the cerebellum to approximately 40% of control levels.
- This reduction in ssCRE-BP activity persisted for at least two weeks following morphine withdrawal.
- Double-stranded CRE binding protein activity in the cerebellum was unaffected by morphine treatment.
- Acute morphine treatment transiently decreased ssCRE-BP activity, with levels returning to baseline within 24 hours.
Conclusions:
- Changes in ssCRE-BP activity are implicated in the development of opiate tolerance and dependence.
- The persistent reduction in ssCRE-BP following chronic morphine exposure suggests a role in long-term adaptations associated with opiate use.