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Tolerance to morphine-induced increases in [14C]catecholamine synthesis in mouse brain
Science (New York, N.Y.)
|December 4, 1970
Summary
Morphine sulfate enhances catecholamine production in mouse brains. Repeated morphine exposure or naloxone administration leads to tolerance, indicated by a rightward shift in the dose-response curve.
Area of Science:
- Neuroscience
- Pharmacology
Background:
- Opioid analgesics like morphine sulfate interact with neurotransmitter systems.
- Catecholamine synthesis is a key pathway affected by opioid drugs.
Purpose of the Study:
- To investigate the effect of morphine sulfate on catecholamine synthesis in the mouse brain.
- To examine the development of tolerance to morphine and the role of antagonists.
Main Methods:
- Utilized carbon-14-labeled tyrosine to trace catecholamine incorporation.
- Administered morphine sulfate repeatedly to induce tolerance.
- Assessed dose-response curves for morphine effects.
- Investigated the impact of naloxone, a morphine antagonist.
Main Results:
- Morphine sulfate significantly increased the incorporation of labeled tyrosine into catecholamines in the mouse brain.
- Repeated morphine administration resulted in a rightward shift of the morphine dose-response curve, indicating tolerance.
- Naloxone, a specific morphine antagonist, also induced a rightward shift in the morphine dose-response curve.
Conclusions:
- Morphine sulfate influences catecholamine synthesis in the brain.
- Tolerance to morphine can be developed through repeated exposure.
- Morphine antagonists like naloxone can modulate the dose-response relationship, suggesting complex interactions within opioid pathways.