Age-related Changes in Astrocytes and Microvasculature in the Median Eminence of the Rat

抄録

Age-related changes in astrocytes, tanycytes and the microvasculature were investigated in the median eminence (ME) of the anterior hypothalamo-hypophyseal system of 2- and 24-month old rats by means of immunocytochemistry and scanning electron microscopy. A computer-assisted image processing system showed a significant increase of the glial fibrillary acidic protein (GFAP) immunoreactivity in the internal layer (IL) and the perivascular region of the external layer (EL) of the ME with age. However, no remarkable changes in either layer could be detected employing vimentin immunoreactivity. An immunoelectron microscopic study revealed that the number of the GFAP-immunoreactive processes markedly increased with age in regions surrounding the capillaries of the EL. Therefore, it may be considered that, in both layers, the astrocytic cell bodies and associated glial processes exhibit a significant increase with age. Investigation of the microvasculature under a scanning electron microscope demonstrated the development and the sinusoidal progress of the external capillary plexus with age, but these changes were not observed in the internal capillary network of the ME. In conclusion, the results of the present study showed a close correlation between the increase of the GFAP-immunoreactive astrocytes and the development of the external capillary plexus. In addition, there was a close correlation between the increase in the GFAP-immunoreactive astrocytes and the sinusoidal progress.