Effects of hindlimb suspension (HS) and ambulation recovery on hippocampal neurogenesis of newly weaned rats were studied by using immunohistochemical techniques. The number of proliferating cell nuclear antigen-positive (PCNA+) cells in the subgranular zone (SGZ) markedly decreased during normal growth. However, neither HS nor subsequent recovery caused additional changes in the number of PCNA+ cells. The number of doublecortin-positive (DCX+) neurons decreased gradually during normal growth. HS resulted in a further decrease in these neurons. However, DCX+ cell numbers became identical to the levels in age-matched controls after 14 days of recovery. PCNA and DCX-double positive cells in the SGZ were also observed, and their cell numbers were not affected by HS and 14-day ambulation. Thus, HS suppressed the generation of DCX+ neurons without affecting PCNA+ cells in the SGZ of weaned rats. Taken together, hippocampal neurogenesis in weaned rats was not severely affected by HS while it decreased significantly as they had grown.
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