A Study of The Effect of Prenatal Exposure to Valproic Acid on The Cerebellum of Albino Rat’s Offspring and The Possible Protective Role of Folic Acid

ABSTRACT
Abstract: Valproic acid (VPA) is used as an anticonvulsant for the treatment of epilepsy. It is also used as one of the mood stabilizing agents in patients with anxiety disorder and as a prophylactic treatment of migraine. The need for anticonvulsant prophylaxis in women of childbearing period is essential since convulsive seizures are considered harmful to the developing embryo. Exposure to VPA during the first trimester of pregnancy was found to be associated with increased risks of several congenital malformations and also in utero exposure to VPA in rats caused cerebellar anomalies.
Folic acid (vitamin B9) is essential for the DNA synthesis and certain biological reactions. Adequate folate intake helped in protection against congenital malformations including neural tube defects.
Aim of the work: To investigate the effect of prenatal exposure to valproic acid on the cerebellum of albino rat’s offspring and to clarify the possible protective role of folic acid.
Material and Methods: Twenty four pregnant albino rats were divided into four groups, six rats each. Group (A); a control group. Group (B); rats received sodium valproate (400 mg/Kg. B.W) starting on gestational day 13 daily till the end of pregnancy by oral gavage. Group (C); rats received folic acid (4 mg/Kg. B.W) starting from first day of pregnancy daily till the end of pregnancy by oral gavage. Group (D); rats received folic acid as in group (C) concomitantly with sodium valproate as in group (B) by oral gavage. At the end of the experiment, six male pups from each group were sacrificed on the postnatal day 14. The cerebella were extracted and processed for light microscopic examination using H&E for paraffin sections and toluidine blue for semi-thin sections. Also immuno-histochemistry technique for glial fibrillar acidic protein (GFAP) was applied to demonstrate astrocytes. Morphometric study was conducted to measure the thickness of cerebellar cortex, count the number of apparently normal Purkinje cells and number of Bergmann cells and calculate GFAP percentage area.
Results: The cerebellar cortex of the control group (A) consisted of three layers; the molecular layer, the Purkinje cell layer and the granular layer. The molecular layer appeared pale with few stellate cells and basket cells. The Purkinje cell layer consisted of Purkinje cells arranged in single row with their oval or flask shaped cell bodies, pale central nuclei and apical cytoplasmic cones. The granular layer consisted of deeply stained rounded small granule cells. This general architecture of the cerebellar cortex was greatly affected in group (B) and an external granular layer was detected on the cerebellar surface in some sections. The Purkinje cells appeared degenerated with pyknotic nuclei and the number of apparently normal cells was statistically decreased compared to control. The number of Bergmann cells was statistically significantly increased. Some granule cells were degenerated with pyknotic nuclei. Also astrocytes showed a strong positive reaction to GFAP with statistically significantly high percentage area compared to the control group. Examination of group (D) showed apparently normal arrangement of layers, Purkinje cells restored their normal flask shaped appearance and arranged in single row with Bergmann glia inbetween. Also astrocytes gave a mild positive reaction to GFAP similar to control group.
Conclusion: Valproic acid (VPA) had degenerative structural effect on the cerebellar cortex if administered during pregnancy. VPA should be administered at the least effective dose and that folic acid co-administration is highly recommended to reduce its toxic effect.