Studies On Age-related Morphological Changes Of Olfactory Bulb To Anterior Piriform Cortex In Cats

The mass of research shows the olfactory degeneration occurs in the old individual people or animal. The paper studied comparatively the morphological structure of the olfactory bulb(OB), the lateral olfactory tract(LOT) and the anterior pyriform cortex (APC)from two age groups of 4 young cats (1~3 years old, 2~2.5kg) and 4 old cats (10~13-years old, 3~3.5kg), in order to explore the morphological and quantitative changes of M-T cells in the OB, and some age-related changes of olfactory transferring path from LOT to APC in cats. We applied such Nissl and immunohistochemical methods as cresylviolet, toluidine bule, anti-NF, anti-S100, anti-GABA, anti-GFAP, and so on to mark the olfactory neurons and their surrounding glial cells, and used a lot of statistical analysis to draw a conclusion on olfactory neurons and their glial cells during senescence, for the sake of discussing simply neural mechanism on the olfactory degeneration from the OB to APC in the course of aging. We concluded that the number and diameter of M-T cells declined significantly; the density of S100-IR cells around them was obviously denser with stronger staining; and the number of NF-IR cells also declined evidently accompanied with neurofibrillary tangles in the OB of old cats. Then, a significant loss of nerve fibers in the LOT especially thicker fibers and a declined diameter of nerve fibers in senile individuals were universal; and an age-related activity increase of S100 protein and decrease of vimentin protein in glial cells of old cats may protect nerve fibers more effectively during aging. What's more, the diameter, density and number of GABAergic neurons in the aged group declined significantly especially in the layersâ…¡andâ…¢of APC; but the change about GFAP-IR cells was justly reversed: old individuals showed clearly larger number and stronger staining of GFAP-IR cells, whose bodies swelled obviously with thicker dendrites especially in the layerâ…¡of APC. All the above suggested those are caused by the ageing that the loss of M-T cells, the decrease of diameter on nerve fibers in the LOT, and the abnormality of GABA content in the APC, which are considered to be a possible mechanism for age-related olfactory function decline from the OB to APC. Besides, the glial hyperplasia in old individuals may play an important role in offering survival neurons nutrition to postpone further ageing.