Numerical analysis of age and gender-dependent neuronal cells in postnatal development of rat hippocampus

The hippocampus, phylogenetically one of the most ancient parts of the central nervous system, is both a highly developed structure of the mammalian brain that plays a role in complex brain functions and one of the brain areas that has continued adult neurogenesis. The aim of the present study was to evaluate the possible changes in volume and the total number of neurons in rat hippocampal regions via a stereological approach.We used 25 Sprague Dawley rats. The animals were housed in groups of five per cage under controlled conditions of constant temperature/humidity and exposed to a 12 h light/dark cycle. The rats were divided into five equally sized groups (n = 5 for each group) according to age and sex as follows: (i) newborn rats (age 0), (ii) one-week male rats, (iii) one-week female rats, (iv) five-week male rats, and (v) five-week female rats. Each of the brain tissues were used for histological examination and stereological analysis.The findings obtained from the current study showed that (i) postnatal development of the hippocampus continues to the adult stage, (ii) development of a large amount of hippocampus is completed after the first postnatal week, and (iii) the female hippocampus exhibits better development in terms of timing, neuron number, and hippocampus volume related to timing.These results suggest that neuronal volumetric development with respect to neuronal number and the postnatal neurogenesis capacity of neural precursors in the hippocampus continues to increase under suitable conditions depending on age and gender.