Dexamethasone receptors and their distribution in the brain of the red tilapia

Cytosolic extracts of liver and brain showed specific, saturable binding with ³H]dexamethasone: Scatchard plots were linear. Cortisol and 11-deoxycortisol acted as competitors, whilst 17,20-dihydroxy-4-pregnen-3-one was relatively much less effective. There was a four-fold range of differences in specific binding capacity between dissected brain regions, the order being telencephalon > hypothalamus > rhombencephalon > optic tectum (thalamus + tegmentum + torus semicircularis) when N_max was calculated in terms of DNA content. There was no evidence for any binding of ³;H]dexamethasone with membrane fractions.