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Prenatal phenytoin exposure decreases neuronal membrane order in rat offspring hippocampus
C V Vorhees1, S L Rauch, R J Hitzemann
1Institute for Developmental Research, Children's Hospital Research Foundation, OH 45229.
Insights
Prenatal phenytoin exposure altered hippocampal membrane fluidity in developing rats, potentially explaining cognitive deficits. This study highlights a specific neurodevelopmental impact of anticonvulsant medication.
Area of Science:
- Neuroscience
- Developmental Toxicology
- Pharmacology
Background:
- Phenytoin is an anticonvulsant medication used to treat epilepsy.
- Prenatal exposure to phenytoin has been associated with developmental abnormalities and cognitive impairments in offspring.
- Understanding the underlying mechanisms of these effects is crucial for risk assessment and management.
Purpose of the Study:
- To investigate the effects of prenatal phenytoin exposure on synaptic plasma membrane order in specific brain regions of developing rats.
- To determine if observed changes in membrane properties correlate with known functional deficits.
Main Methods:
- Pregnant Sprague-Dawley rats were administered phenytoin (200 mg/kg) or vehicle from days 7-18 of gestation.
- Offspring were assessed at postnatal days 3 and 28.
- Synaptic plasma membrane order was measured using fluorescence polarization with 1,6-diphenyl-1,3,5-hexatriene (DPH) in cerebellum, cortex, and hippocampus.
Main Results:
- No significant differences in membrane anisotropy were observed in 3-day-old offspring.
- A significant reduction in hippocampal synaptic plasma membrane anisotropy was found in 28-day-old phenytoin-exposed offspring.
- This effect was region-specific, with no changes noted in the cerebellum or cortex at 28 days.
Conclusions:
- Prenatal phenytoin exposure leads to altered hippocampal membrane fluidity in developing offspring.
- This membrane disordering effect in the hippocampus may underlie the previously observed memory impairments.
- The findings support a link between anticonvulsant exposure, neurochemical changes, and functional deficits.
Abstract:
Pregnant Sprague-Dawley CD rats were administered 0 or 200 mg/kg of phenytoin by gavage on days 7-18 of gestation, with controls pair-fed to the phenytoin exposed dams. At birth, litter sizes were standardized to 10, balancing for sex, and were reared by their biological dams until either day 3 or 28. At each of these ages half of the litters from each group were used to determine synaptic plasma membrane order in selected brain regions (cerebellum, cortex, hippocampus) by fluorescence polarization using the probe 1,6-diphenyl-1,3,5-hexatriene (DPH). No significant differences in membrane anisotropy were noted in 3-day-old phenytoin offspring, but a reduction in anisotropy in 28-day-old phenytoin offspring hippocampal regions was observed. The effect was specific in that no changes were found in the cerebellum or cortex at this age. The magnitude of the change corresponded to an approximately 3-5 degrees C increase in temperature and to changes produced by other known membrane disordering agents, such as ethanol. The data, together with previous findings of memory impairments in phenytoin offspring, support an association between the hippocampal membrane disordering effect and functional impairments produced by prenatal phenytoin exposure.