Table 2.

Selected measurements of endogenous steroid levels in adult male rat plasma or serum (ng/ml) and brain tissue (ng/g).

Steroid	Plasma/serum	Cortex	Hippocampus	Hypothalamus	Cerebellum	Whole brain
Pregnenolone	n.d.–0.9	0.4–7.0	4.8	11–12	0.4–19	1.7–4.9
Progesterone	0.5–2.2	1.5–7.0	4.6	0.9	0.7–5.3	0.4–0.7
DHEA	n.d.–0.1	0.2	0.1	1.5	0.2	0.2–0.3
Testosterone	1.2–4.2	0.1–2.6	4.9	14	2.3–2.4	1.4–2.2
17β-Estradiol	n.d.–0.004	0.1	2.3	n.a.	0.02	n.d.
5α-DHT	n.d.–0.2	n.d.–0.2	1.9	2.0	0.1	n.d.
Corticosterone	20–54	7.5	44	43	20	4.6–50

All brain steroid measurements were obtained after solid phase extraction. In some cases, steroid extracts were further purified using high-performance liquid chromatography, gas chromatography, or thin-layer chromatography. Steroids were quantified using radioimmunoassay or mass spectrometry. DHEA, dehydroepiandrosterone; 5α-DHT, 5α-dihydrotestosterone; n.d., non-detectable; n.a., not assessed. Values compiled from Butte et al. (1972); Robel et al. (1973); Lanthier and Patwardhan (1987); Purdy et al. (1991); Korneyev et al. (1993b); Wang et al. (1997); Vallée et al. (2000); Ebner et al. (2006); Meffre et al. (2007); Caruso et al. (2008); Hojo et al. (2009); Pesaresi et al. (2010).