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Morphine-induced alterations on DNA-binding proteins in developing rat brain
Z Tencheva1, A Velichkova, A Angelova
1Brain Research Institute, Bulgarian Academy of Sciences, University of Sofia, Bulgaria.
Abstract:
Endogenous opioids and opiate drugs inhibit nervous system maturation through both direct and indirect mechanisms. Recently much attention has been directed toward changes in the postreceptor events and it has been speculated that the regulation of gene expression may be involved in the development of drug tolerance and dependence. We investigated the changes in the levels of in vitro RNA synthesis in developing rat brain after continuous block of opioid receptors. Repeated naloxone treatment induced increased levels (27-48%) of RNA synthesis during the early postnatal period. Using mobility gel shift assay the presence of octamer binding proteins (Oct-1) and the replication differentiation transcription factor CTF/NF1 in the developing rat brain were studied both after single or repeated morphine and naloxone treatment. Decreased Oct-1 binding activity in brain protein extracts 1 h after morphine application was registered, while opioid antagonist naloxone exerted an opposite effect on this octamer protein following single drug treatment. Repeated administration of morphine or naloxone decreased markedly the DNA-binding affinity of Oct-1. The binding activity of CTF/NF1 changes differently showed higher levels assessed 30-120 min after morphine administration. The opposite trend of the changes in opiate drug and opioid antagonist animals suggests opioid receptor-mediated regulation of Oct-1 and CTF/NF1 transcription factors.
Insights
Opioid drugs affect nervous system development by altering gene expression. Research shows repeated naloxone or morphine treatment changes RNA synthesis and transcription factor activity in developing rat brains, suggesting opioid receptor involvement.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Opioid drugs and endogenous opioids influence nervous system maturation via complex mechanisms.
- Postreceptor events and gene expression regulation are implicated in opioid tolerance and dependence.
- Developing rat brain is a model to study opioid effects on neural maturation.
Purpose of the Study:
- To investigate the impact of continuous opioid receptor blockade on RNA synthesis in the developing rat brain.
- To examine changes in transcription factor binding activity (Oct-1 and CTF/NF1) following acute and chronic morphine and naloxone administration.
- To elucidate the role of opioid receptor-mediated regulation in controlling these transcription factors.
Main Methods:
- In vitro RNA synthesis assays were performed on developing rat brain extracts.
- Mobility gel shift assays were used to study DNA-binding activity of Oct-1 and CTF/NF1.
- Animals received single or repeated treatments of morphine (opioid agonist) or naloxone (opioid antagonist).
Main Results:
- Repeated naloxone treatment increased RNA synthesis levels by 27-48% in early postnatal development.
- Morphine decreased Oct-1 binding activity acutely, while naloxone showed an opposite effect.
- Both repeated morphine and naloxone treatments significantly reduced Oct-1 DNA-binding affinity.
- CTF/NF1 binding activity increased after morphine administration, indicating differential regulation.
Conclusions:
- Opioid receptor blockade and agonist/antagonist treatments differentially regulate RNA synthesis and transcription factor activity in the developing brain.
- The observed changes in Oct-1 and CTF/NF1 suggest opioid receptor-mediated control over these key regulatory proteins.
- These findings contribute to understanding the molecular mechanisms underlying opioid effects on nervous system development and adaptation.