Changes of Doublecortin-Immunoreactive Cells from the Acute Phase to Chronic Phase After Transient Global Brain Ischemia in Rat Cingulate Cortex

Doublecortin (DCX)-immunoreactive (-ir) cells play important roles in adult cortical remodeling. We previously reported that DCX-ir cells decrease after transient global brain ischemia (GBI) in the cingulate cortex (Cg) of rats. In the present study, we examined the changes of DCX-ir cells from the acute to the chronic phase after GBI in rats. Transient GBI was induced by a four-vessel occlusion model as described previously. Thirty-six rats were divided into six groups: day 7 after sham operation (Group Sham+A), day 7 after 3 min GBI (Group GBI3+A), day 7 after 10 min GBI (Group GBI10+A), day 90 after sham operation (Group Sham+C), day 90 after 3 min GBI (Group GBI3+C), and day 90 after 10 min GBI (Group GBI10+C). The numbers of DCX-ir cells per unit area (mm2) were investigated in the anterior cingulate cortex (ACC) and retrosplenial cortex (RS). A two-way factorial analysis of variance regarding the time of GBI (sham, GBI3, GBI10) or the period after GBI (day 7, day 90) was employed in each area. Regarding the time of GBI, there were significant differences in both the ACC and the RS (p < 0.001, respectively). Regarding the period after GBI, there was no significant difference in the ACC, whereas a significant difference was found in the RS (p = 0.005). In each area and in each phase, the numbers did not change in GBI3 (one-way ANOVA followed by a Tukey test) and decreased in GBI10 (p < 0.005). The numbers in the RS from the acute phase to chronic phase did not change in the sham and GBI3, and decreased in GBI10 (independent t-test, p < 0.001). However, histochemical staining with Fluoro-Jade B suggested that neuronal cell death did not occur in both the ACC and the RS in all groups. The present findings indicate that the cortical remodeling potential in the Cg decreases in the acute phase after GBI, and continues to decrease until the chronic phase.