EFFECTS OF ADRENALECTOMY AND GLUCOCORTICOIDS ON RAT-BRAIN DOPAMINE-RECEPTORS

The effects of adrenalectomy (ADX) and dexamethasone (DEX) treatment o n brain dopamine (DA) receptors of ovariectomized (OVX) rats were inve stigated by autoradiography using binding of the D1 and D2 antagonists ligands [H-3]SCH 23390 and [H-3]spiperone, respectively. Fourteen day s after ADX, D1 receptors decreased in the middle striatum (M.CPu) and in the dorsal area of the posterior striatum (P.CPu). A more pronounc ed decrease was observed in the substantia nigra (SN) and no significa nt changes occurred in the anterior striatum (A.CPu), globus pallidus (GP) and accumbens (Acb). D2 receptors decreased in the M.CPu and dors al area of the P.CPu and remained unchanged in the A.CPu as compared t o OVX rats. Twenty-eight days after ADX, D1 and D2 receptors decreased in the A.CPu (D2), in the M.CPu (D2) and substantially in the SN (D1) . DEX treatment (14 days, 0.5 mg/kg, b.i.d., IM, starting 14 days afte r ADX) reversed these effects in the A.CPu (D2), M.CPu (D2) and SN (D1 ) when compared to ADX + OVX rats. DEX also increased the density of D 1 receptors in Acb, A.CPu and M.CPu when compared to OVX rats. Striata l homogenates of rats treated chronically with ACTH and corticosterone had an increased density of D1 receptors while these treatments alone left these receptors unchanged, thus suggesting either a minor role o r no role of the changes in ACTH levels following glucocorticoids mani pulations. Our results suggest that the adrenals play a role in the mo dulation of DA receptors activity in the rat brain.