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Published on: July 29, 2014
Ultrastructural changes in rat locus coeruleus induced by chronic opioids
1Institute of Pharmacology and Toxicology, Academy of Military Medical Science, Beijing, China.
Acta Neuropathologica
|August 1, 1997
Summary
Chronic morphine use significantly damages locus coeruleus (LC) neurons, causing ultrastructural injury. Dihydroetorphine, a different opioid, induced only minor changes, suggesting LC neurons are more vulnerable to morphine.
Area of Science:
- Neuroscience
- Pharmacology
- Cell Biology
Background:
- The locus coeruleus (LC) is a critical noradrenergic nucleus in the brain.
- Opioids chronically regulate LC neuron activity, but their morphological effects are poorly understood.
Purpose of the Study:
- To investigate the ultrastructural changes in rat LC neurons following chronic morphine or dihydroetorphine treatment.
- To compare the neurotoxic potential of morphine and dihydroetorphine on LC neuron ultrastructure.
Main Methods:
- Rats received daily subcutaneous injections of saline, morphine, or dihydroetorphine for 5 days.
- Withdrawal was precipitated in some animals using naloxone.
- Ultrastructure of the LC was analyzed using electron microscopy.
Main Results:
- Chronic morphine treatment caused significant injury to LC neurons, including nuclear indentation and endoplasmic reticulum fragmentation.
- Morphine also led to myelinoid bodies in processes and presynaptic vesicle accumulation.
- Naloxone-precipitated withdrawal did not reverse morphine-induced neuronal injury.
- Dihydroetorphine induced only minor ultrastructural changes in LC neurons.
Conclusions:
- LC neurons exhibit greater vulnerability to chronic morphine exposure compared to dihydroetorphine.
- Morphine-induced ultrastructural damage to LC neurons is substantial and not fully reversed by naloxone-precipitated withdrawal.
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