DEXAMETHASONE RECEPTORS AND THEIR DISTRIBUTION IN THE BRAIN OF THE RED TILAPIA

Cytosolic extracts of liver and brain showed specific, saturable bindi ng with [H-3]dexamethasone: Scatchard plots were linear. Cortisol and 11-deoxycortisol acted as competitors, whilst 17 alpha,20 alpha-dihydr oxy-4-pregnen-3-one was relatively much less effective. There was a fo ur-fold range of differences in specific binding capacity between diss ected brain regions, the order being telencephalon > hypothalamus > rh ombencephalon > optic tectum approximate to (thalamus + tegmentum + to rus semicircularis) when N-max was calculated in terms of DNA content. There was no evidence for any binding of [H-3]dexamethasone with memb rane fractions.