Adrenal steroid-induced changes in beta-adrenergic receptor binding in rat hippocampus

Bilateral 6-hydroxydopamine (6-OHDA) lesions of the dorsal noradrenergic bundle have been shown to increase [3H]dihydroalprenolol (DHA) binding in the rat hippocampus. The effect of adrenalectomy on this increase in receptor binding was examined. Groups of rats received stereotaxically placed 6-OHDA injections aimed at the dorsal bundle (DB) or vehicle injections (control). Half of each group subsequently received bilateral adrenalectomies (ADX) and the other half received sham operations, yielding four groups: control, DB, ADX, and DB + ADX. The DB lesions produced a 41% increase in maximum binding in close agreement with a previous report. No statistically significant change in [3H]DHA receptor binding was observed following adrenalectomy treatment alone. By contrast, the DB + ADX group showed a significant increase in maximum [3H]DHA receptor binding compared to the DB group. This adrenalectomy-induced increase was reversed after 1 week of corticosterone treatment (1.0 mg/kg/12 h, s.c.). These results suggest an interaction between noradrenergic mechanisms and corticosterone in the hippocampus.