Mineralocorticoids and glucocorticoids cooperatively increase salt intake and angiotensin II receptor binding in rat brain

Mineralocorticoids, such as deoxycorticosterone acetate (DOCA), and angiote nsin II (AngII) act synergistically in the brain to elicit salt appetite. G lucocorticoids, such as dexamethasone (DEX), also may enhance the behaviora l effects of DOCA and AngII. However, the brain regions involved in these b ehavioral interactions have not been elucidated. This study tested the hypo thesis that DEX potentiates the effects of DOCA on Angll binding, especiall y at the AT1 receptor. We confirmed that DEX potentiated the effects of DOC A on salt appetite. Concomitantly, steroid-specific and region-specific cha nges in AT1 binding were noted. Specifically, in the hypothalamic paraventr icular nucleus, treatment with DEX or DOCA + DEX increased AT1 binding. In the subfornical organ (SFO) and area postrema, there was an increase in AT1 binding when both steroids were combined, but not when given individually. However, there was no change in AT2 binding in any brain region studied an d no change in AT1 or AT2 binding to either receptor subtype in the pituita ry. The results indicate that DOCA and DEX may increase the sensitivity of the brain to the behavioral and physiological actions of Angll by upregulat ing AT1 receptors in the SFO and area postrema.