Effect of valproic acid administration during pregnancy on postnatal development of cerebellar cortex and the possible protective role of folic acid

Background: Valproic acid (VPA), one of the most important antiepileptic drugs, proved to be inevitable for epileptic pregnant women to limit the hazards of convulsions on the foetuses and mothers. Periconceptional folic acid supple­mentation was investigated to protect against several birth defects. However, its role against VPA cerebellar toxicity was not properly investigated. The present study was conducted to evaluate the protective effect of folic acid against VPA cerebellar neurotoxicity.

Materials and methods: Twenty-four pregnant female albino rats were divided into three groups; group I (control group, did not receive any drugs), group II (given VPA at a dose of 50 mg/kg body weight once daily) and group III (given the same dose of VPA and 400 μg/kg of body weight folic acid once daily). Ten male offspring from each group were sacrificed at two ages: at 2 and 12 weeks after birth. Samples of cerebellar cortex were taken and prepared for light, electron microscopic examination, glial fibrillary acidic protein (GFAP) immunohistochemical study and histomorphometric analysis.

Results: The present study confirmed the neurotoxic effect of prenatal VPA on the cerebellar cortex, especially on Purkinje cells. The cells appeared shrunken, reduced in density, disorganised and surrounded by empty haloes. Nuclear damage and axon degeneration in the form of vacuolation, loss of organelles and absence of neurofilaments with myelin sheath depletion were detected. Concomitant supply of folic acid was shown to retain the normal architecture of Purkinje cells with their axons and nuclei. In many animals receiving folic acid, the thickness of all layers of the cortex increased up to that of the control groups, after being markedly reduced in VPA-treated groups. GFAP immunoreaction was also improved against the strong positive gliosis detected in VPA-treated groups.

Conclusions: The present study confirmed the protective role of folic acid against the cerebellar neurotoxic effects of VPA prenatal exposure. It is recommended that folic acid supplements should be given to every epileptic pregnant mother treated with VPA. (Folia Morphol 2018; 77, 2: 201–209)

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