Introduction: In recent years, deterioration in cognitive, learning, and memory become one of the significant problems in human life. Hippocampus is a pivotal part of the brain's limbic system which serves a critical role in memory, learning process and regulating the emotions. In most regions of the brain, neurons are generated only at specific periods of early development, and not born in the adulthood. In contrast, hippocampal neurons are generated throughout development and adult life.
Aim of the Study: Was to assess the postnatal development of the hippocampal formation.
Material and Methods: Twenty-four male albino pups were divided into four groups. Ages day 1, week 1, week 2 and week3, all the pups were sacrificed; the brain were dissected and processed for histological and morphometric methods.
Results: The general architecture of the hippocampus proper with its polymorphic, pyramidal, and molecular layers was present at day1, whereas the details of the adult structure appeared at week 2. There was a statistically significant increase in the thickness of the PL of the CA1 in group II compared to group I. There was a statistically non-significant increase in the number of pyramidal cells of CA1 in group II compared to group I, while in group IV there was a statistically non-significant decrease in number of cells compared to group III.
Conclusion: The important sequences of events in the growth and maturation of the hippocampal formation in male albino rat occurred in the first 2 postnatal weeks. In addition, the period of weaning in group IV(week3) and mother separation could affect negatively the maturity of the hippocampus at this period in a form of increase apoptosis of pyramidal cells.