Protective Effect of Curcumin on the Density of Hippocampal Dark Neurons In Mice Model of Aging Induced by D-galactose: A Histopathological Study

Curcumin is the most active ingredient in turmeric root of Curcuma longa of the Zingiberaceae family and has a potent antioxidant activity. This study aimed at investigating the effects of curcumin with various doses on the density of dark neurons in the hippocampus of induced D-galactose aging mice model. This experimental study was conducted on 40 adult male BALB/c mice. We randomly divided animals into 5 groups: D-galactose, control, and curcumin 1, curcumin 2, and curcumin 3 groups. D-galactose (300 mg/kg) was intraperitoneally injected into the D-galactose group for 6 weeks. D-galactose and doses of 25, 50, and 100 mg of curcumin were administrated, respectively, to the curcumin groups 1 to 3 every day for 14 days. After 6 weeks, the mice's brains were stained with toluidine blue after tissue passage. Then, the mean dark neuron volume density in each unit of the ​​tissue was assessed using stereological formulas. The obtained data were analyzed by Analysis of variance (ANOVA) in SPSS. Compared with the control group, the average number of dark neurons in the hippocampus significantly increased following the administration of D-galactose (P = 0.001). The average dark neurons frequency in the hippocampus significantly decreased in the 50 and 100 mg/kg curcumin-treated groups (P=0.001 for both) compared to that of the D-galactose treated animals. The results of this study showed that treatment with 100 mg/kg of curcumin reduced the number of dark neurons in the hippocampus of the aging mice. It seems that curcumin decreases dark neurons via the reduction of apoptosis. Also, curcumin is a powerful antioxidant and affects the level of antioxidant status in the brain.