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Endogenous opioid systems and neural development: ultrastructural studies in the cerebellar cortex of infant and
1Department of Anatomy, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
Abstract:
Endogenous opioid systems participate in regulating the development of the nervous system. Opioid antagonists like naltrexone (NTX) perturb the relationship between endogenous opioids and opioid receptors quite effectively and reveal the function(s) of endogenous opioid systems during neuro-ontogeny. In this study, the effects of NTX, as well as the repercussions of modulation of endogenous opioid systems during critical stages of neural ontogeny, have been examined at the electron microscopic level of resolution in infant (10 day) and weanling (21 day) rats. Preweaning rats were subjected to complete (50 mg/kg NTX) or intermittent (1 mg/kg NTX) daily receptor blockade. Extensive ultrastructural examinations were conducted on the external germinal (granule), molecular, Purkinje, internal granule, and medullary layers of the cerebellar cortex. The NTX groups had striking similarities in morphology to that of controls at postnatal days 10 and 21. These results support the hypothesis that endogenous opioid systems act as trophic factors as they regulate growth; their effects on cell growth and survival, however, do not alter the basic ultrastructural morphology of the cells. Moreover, these data further strengthen the validity of paradigms utilizing opioid antagonists to explore the relationship of endogenous opioid-opioid receptor interactions and neural morphogenesis.
Insights
Naltrexone (NTX) treatment did not alter the basic ultrastructure of developing rat cerebellar cells. This suggests endogenous opioid systems regulate cell growth but not fundamental cell morphology during neurodevelopment.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- Endogenous opioid systems play a role in nervous system development.
- Opioid antagonists, such as naltrexone (NTX), can be used to study these systems.
- Understanding opioid system functions during neuro-ontogeny is crucial.
Purpose of the Study:
- To examine the effects of naltrexone (NTX) on neural development.
- To investigate the role of endogenous opioid systems in neuro-ontogeny.
- To analyze ultrastructural changes in the rat cerebellum following opioid receptor blockade.
Main Methods:
- Infant and weanling rats (10 and 21 days old) received complete or intermittent naltrexone (NTX) daily.
- Ultrastructural examinations were performed on various cerebellar cortex layers.
- Morphological comparisons were made between NTX-treated and control groups.
Main Results:
- No significant differences in cerebellar cell ultrastructure were observed between NTX-treated and control rats.
- Both complete and intermittent NTX treatments yielded similar morphological results.
- Cellular morphology remained consistent across different experimental conditions.
Conclusions:
- Endogenous opioid systems may function as trophic factors regulating cell growth and survival.
- Opioid system modulation does not appear to alter fundamental cellular ultrastructure.
- Opioid antagonists are valid tools for studying opioid-receptor interactions in neural morphogenesis.