POSTNATAL DEVELOPMENT OF MICROGLIA - AN IMMUNOHISTOCHEMICAL INVESTIGATION IN THE RAT

Microglia are glial cells that originate from the monocyte-macrophage system and perform immune functions in the brain. They are found all over the CNS, mainly around blood vessels. Microglial activation is a known factor in the pathogenesis of conditions such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, ischemic and traumatic brain injury. Moreover, in the last years mounting evidence has implicated physiological roles of microglia in intact CNS. The aim of the present study is qualitative and quantitative analysis of microglial population in immunohistochemically stained brains and spinal cords of male white Wistar rats during postnatal development. After perfusion fixation and cryoprotection, freezing microtome sections of rat brains and spinal cords were further processed by Iba 1 immunohistochemistry and applying the avidin-biotin (ABC) method. Computer-assisted image analysis was applied to the light microscopic preparations obtained. Microglial cells were found distributed throughout all brain and spinal cord structures. However, the immunoreactivity (AF) and the microglia cell densities (CD) differ between the different brain and spinal cord zones as well as during development in the same structure. After birth the immunoreactivity and the microglial cell density are low in all structures followed by a significant rise in their levels that reached a peak on the tenth day with a subsequent decrease till the values at the end of the third month. The parallel appearance of both AF and CD curves suggests that rnicroglial cell size does not experience dramatic changes in the postnatal development. In conclusion, microglial population is a dynamic cell group with characteristic changes during development, which should be taken into account in future researches in the field of brain pathology and physiology.