Fig. 6

Hypercapnia aggravates apoptosis of hippocampal neurons of hypoxemic rats (n = 4). a The immunoreactive bands of caspase-3 (17 kDa) and GAPDH (36 kDa). b There is a significant interaction effect between hypercapnia treatment and hypoxia treatment (P < 0.05). c Simple effects analyses show that the protein expression levels of caspase-3 in hypercapnia group have no significant difference compared with S group (ns P > 0.05). A significant increase in caspase-3 expression is observed in hypoxemia group compared with S group (**P < 0.01). The levels of caspase-3 expression in HH group is the highest as compared to hypercapnia group (**P < 0.01) and hypoxemia group (**P < 0.01). d Immunofluorescence images show the expression of caspase-3 (B, E, H, K, red), NeuN⁺ neurons (A, D, G, J, green), and the co-localization of caspase-3 and neurons (C, F, I, L). The results also show that hypercapnia alone is not enough to increase the expression of caspase-3. The expression of caspase-3 in neurons in the hypoxic hippocampus is markedly increased. Additionally, the expression of caspase-3 is further enhanced following treatment of hypercapnia in the hypoxic hippocampus. Scale bars: (A-L), 20 μm. S group sham-operated group, HH group hypercapnia + hypoxemia group. The concentrations of CO₂ and O₂ in the air are 0.03 and 21%, respectively