Figure 6.

The neurogenic property of APα is specific and not shared by isomers or other steroids in the biosynthetic pathway. Rat hippocampal neurons were loaded with 1 μCi/ml [³H]thymidine in the presence or absence of the indicated neurosteroids at 37°C for 24 h. APα induced a 150% increase in [³H]thymidine incorporation relative to control. Moreover, DNA synthesis was specific to APα compared with other structurally and chemically similar steroids. P₄, the precursor molecule to APα, also induced a modest increase in [³H]thymidine incorporation; however, the stereoisomers of allopregnanolone, epiallopregnanolone, and APβ, as well as 5α-pregnan-3β-ol, were without effect. Additionally, allopregnanediol, allopregnantriol, and pregnenolone sulfate induced a significant decrease in [³H]thymidine incorporation. Data are expressed as mean ± SEM. ^*p < 0.05; ^**p < 0.01; ^***p < 0.001.