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Exposure to perinatal morphine promotes developmental changes in rat striatum
A Gorio1, M L Malosio, L Vergani
1Laboratory for Research on Pharmacology of Neurodegenerative Disorders, Department of Medical Pharmacology, Milano, Italy.
Insights
Perinatal morphine exposure alters brain development in rats, affecting neurotransmitters like dopamine and serotonin. Naltrexone treatment reversed these morphine-induced developmental changes, implicating opioid receptors.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- Perinatal exposure to opioids can impact neurodevelopment.
- Opioid receptors play a critical role in brain development and function.
Purpose of the Study:
- To investigate the long-term effects of perinatal morphine exposure on neurochemical development in the rat striatum.
- To determine the role of opioid receptors in mediating these developmental changes.
Main Methods:
- Administered morphine to pregnant rats and their offspring.
- Analyzed neurotransmitter and neuropeptide levels (substance P, met-enkephalin, dopamine, serotonin) and their corresponding mRNA expression in offspring.
- Assessed the effects of naltrexone co-administration.
Main Results:
- Perinatal morphine exposure led to sustained changes in striatal substance P and met-enkephalin concentrations and altered prometenkephalin A mRNA expression.
- Increased dopamine metabolism and reduced tyrosine hydroxylase mRNA expression in the substantia nigra were observed.
- Serotonin levels were transiently reduced in early postnatal life.
- Naltrexone treatment prevented these neurochemical alterations, confirming the involvement of opioid receptors.
Conclusions:
- Perinatal morphine exposure induces significant and lasting neurodevelopmental alterations in the rat brain.
- Opioid receptor signaling is critically involved in mediating the neurochemical and developmental consequences of perinatal morphine exposure.
- These findings highlight the vulnerability of the developing brain to opioid exposure and the potential for therapeutic intervention with opioid antagonists.
Abstract:
This study shows that perinatal exposure to morphine promotes developmental changes (up to 8 months of life) in the striatum by up-regulating concentrations of substance P and met-enkephalin with changes of prometenkephalin A mRNA expression at the day of birth only. Dopamine metabolism (up to 60 days) is also increased as suggested by the reduced concentrations of dopamine and increased content of 3,4-dihydroxyphenylacetic acid. Tyrosine hydroxylase mRNA expression is selectively reduced only in the substantia nigra by perinatal morphine. Serotonin content is reduced only during the early postnatal days and is unaffected thereafter. Supplementation of naltrexone to morphine-exposed rats prevents monoaminergic and neuropeptidergic changes in the striatum, which directly implicates opioid receptors in the developmental changes caused by morphine. The data suggest that perinatal morphine may inhibit met-enkephalin release, causing accumulation of the peptide without corresponding changes in specific mRNA. Dopamine release may also be increased as indicated by a higher metabolism and consequent reduction of tyrosine hydroxylase mRNA expression in the substantia nigra.