GLUCOCORTICOID REGULATION OF MESSENGER-RNA ENCODING (NA-BRAIN MEASURED BY IN-SITU HYBRIDIZATION(K)ATPASE ALPHA(3) AND BETA(1) SUBUNITS IN RAT)

The effect of glucocorticoids on (Na + K)ATPase mRNA synthesis was stu died in 19 brain areas of adrenalectomized (ADX) rats untreated or rec eiving dexamethasone (DEX). For in situ hybridization, we employed a [ S-35]oligonucleotide probe for the alpha(3)-subunit isoform, and a [H- 3]cDNA coding for the beta(1)-subunit of the enzyme. Mean levels of gr ain density for the alpha(3) subunit mRNA of DEX-treated rats were sig nificantly higher by a 't' test in medial septum, amygdala lateralis ( AL) and medialis (AME), gyrus dentatus, CA(4) hippocampal area, substa ntia nigra and periventricular gray, compared to untreated rats. For t he beta(1)-subunit, mean levels after DEX were significantly higher in AL and lateral preoptic area. In addition, the Kolmogorov-Smirnov tes t applied to frequency histograms of neuronal densities indicated a co ordinate increase in alpha(3) and beta(1)-subunit mRNA expression for the CA(2) subfield and preoptic area medialis (POA MED). We conclude t hat (1) glucocorticoids are positive modulators of (Na + K)ATPase mRNA ; (2) analysis of frequency histograms suggests that glucocorticoids p romote in a few regions (AL, POA MED, CA(2) subfield) a coordinate inc rease in the biosynthesis of the alpha(3) and beta(1)-subunit mRNA. In 11 other areas stimulation occurs for one subunit mRNA only, whereas 5 areas were insensitive to glucocorticoid effects on this enzyme.