Fig. 4.

R_CorrTissue% (ml × 100 g⁻¹) of [³H]cortisol in the absence and presence of unlabeled corticosterone in wild-type mice using in situ brain/choroid plexus perfusion technique. [³H]cortisol (3.6 nm), along with [¹⁴C]sucrose (vascular space marker; 0.5–1.0 nm), was administered by a slow-drive syringe pump into the artificial plasma containing unlabeled corticosterone (30 or 300 μm), dissolved in methanol. After a perfusion time of 20 min, the mouse was decapitated, and selected brain regions (open white bar, frontal cortex; light gray bar, hippocampus; closed black bar, hypothalamus; dark gray bar, cerebellum) (A) and choroid plexus and pituitary gland (open white bar, choroid plexus; closed black bar, pituitary gland) (B) were sampled. The concentration of [³H] or [¹⁴C] radioactivity in the tissues (dpm g⁻¹) is expressed as a percentage of that in the artificial plasma (dpm ml⁻¹). The uptake of [³H]cortisol in the hypothalamus and in the cerebellum was significantly increased in the presence of 300 μm of unlabeled corticosterone (P = 0.013 and P = 0.020, respectively, Bonferroni t test, after one-way ANOVA, vascular space corrected) compared with methanol controls. The uptake of [³H]cortisol in the pituitary gland was significantly decreased in the presence of 300 μm of unlabeled corticosterone compared with methanol controls (P = 0.024, Kruskal-Wallis ANOVA on ranks), (n = 12–14). *, Significant difference (P < 0.05) compared with methanol controls.