ABSTRACT
Although the anatomy of the adult mammalian hippocampus has been studied extensively, few reports have dealt with hippocampal cytogenesis and morphogenesis. Moreover, the capillary network, which is the functional component of the vascular bed in terms of tissue metabolic requirements has not been studied during postnatal development of the rat hippocampus. To follow the postnatal development of the capillaries in the rat hippocampal formation in view of the temporal variation in the development of its regions using morphometric parameters. A sample of 37 rats was used, quantitation of the capillaries in four hippocampal regions [subiculum, regio superior, regio inferior, and dentate gyrus] at different postnatal ages [P1, 3, 5, 7, 10, 14, and 21 days] was performed using computer-aided morphometry of alkaline phosphatase positive capillary profiles. Capillary diameter, length/volume density, and intercapillary distance were measured on 30
m-thick frozen coronal sections after controlled fixation. There was a decrease in capillary diameter and in intercapillary distance, with a concomitant increase in capillary length density in all hippocampal regions at the second postnatal week [P10]. While the intercapillary distance was significantly reduced during the second postnatal week in all regions; however, its value during the first postnatal week was at its maximum in the dentate gyrus, minimum in the subiculum, and in between both in region superior and inferior. Capillary morphometric parameters were coincidental with the metabolic activity and volumetric growth during postnatal development. It appeared that [P10] was a decisive milestone in the growth of the hippocampal capillary network, at which capillary parameters indicated a significant increase in capillary sprouting and permeation. The repertoire of the changes in intercapillary distance was a replica of the volumetric proportional expansions of the hippocampal regions. The mean intercapillary distance was considered as the most sensitive microvascular parameter