THE EFFECT OF PRENATAL EXPOSURE TO VALPROIC ACID ON BASOLATERAL NUCLEUS OF AMYGDALA OF RAT OFFSPRINGS: HISTOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY

Background: The amygdala plays a key role in the emotional process, the development of social behavior and reward learning. Aim of the Work: to study the structural and morphometric changes of the amygdala of rat's offsprings following maternal exposure to valproic acid. Material and methods: 12 pregnant female rats were used in the current study divided equally into two groups; control group and valproic acid treated group (received 500 mg/kg body weight valproic acid) by oral gavage on day 11 and 13 of pregnancy. At the end of pregnancy five male newborn rats were sacrificed at week 1, 2 and 3 of the experiment respectively from the two groups. Histological, morphometric & immunohistochemical studies were performed and the results were statistically analyzed. Results: control group showed the stages of development of basolateral nucleus of amygdala. There was significant increase of surface area of basolateral nucleus. This could be explained by significant increase in the number of oligodendroglia that was associated with apparent expansion of neuropil and vasculatures. In valproic acid treated groups many neurons showed degenerative changes during first week. However, during second week, there was apparent increase in the total cell number indicating compensatory neurogenesis. In the third week, many ghost cells appeared reflecting failure of compensatory mechanism and impairment of microglia function. This resulted in astrocytes activation Conclusion: Results of the present study demonstrated structural changes of the rat amygdala across the first three weeks of postnatal life. This study also explored the devastating effect of the prenatal exposure to valproic acid on the structure of the amygdala started by neuronal death on the first week and end with gliosis particularly in the third week of age postnatally.