Fig. 1.

Main biochemical pathways for neurosteroidogenesis in the vertebrate brain. Boxes represent neurosteroids which are sensitive to modulation by AD key proteins, Aβ and/or tau. Mitochondrial 17β-HSD (marked by *) is equivalent to the ABAD in mitochondria. PREG pregnenolone, PROG progesterone, 17OH-PREG 17-hydroxypregnenolone, 17OH-PROG 17-hydroxyprogesterone, DHEA dehydroepiandrosterone, DHP dihydroprogesterone, ALLOPREG allopregnanolone, DHT dihydrotestosterone, P450scc cytochrome P450 cholesterol side chain cleavage, P450c17 cytochrome P450c17, 3β-HSD 3β-hydroxysteroid dehydrogenase, 5α-R 5α-reductase, Arom. aromatase, 21-OHase 21-hydroxylase, 3α-HSOR 3α-hydroxysteroid oxydoreductase, 17β-HSD 17β-hydroxysteroid dehydrogenase