CHRONIC CORTICOSTERONE TREATMENT ELICITS DOSE-DEPENDENT CHANGES IN MOUSE-BRAIN ALPHA-BUNGAROTOXIN BINDING

Previous studies have shown that adrenalectomy results in a small incr ease in hippocampal alpha-bungarotoxin binding, whereas seven days of chronic treatment with high doses of corticosterone results in decreas es in alpha-bungarotoxin binding in several brain regions. The studies reported here examined the effects of different doses of corticostero ne on brain alpha-bungarotoxin binding. C3H mice were adrenalectomized and treated with corticosterone-containing pellets (0.5-60%) for four days, alpha-Bungarotoxin binding was measured in eight brain regions. Chronic treatment with corticosterone resulted in plasma corticostero ne levels ranging from the low levels observed in an unstressed mouse during the daytime to levels significantly above those observed in mic e during the night or as a result of stress. Adrenalectomy resulted in small increases in binding in hippocampus which was reversed by low d ose corticosterone treatment. Chronic high-dose corticosterone treatme nt resulted in significant decreases in binding in four of the eight b rain regions examined. Similar, but not identical, results were obtain ed in two other mouse strains (C57BL and DBA/2). These results argue t hat corticosterone levels play an important role in modulating the lev el of the brain nicotinic receptors that bind alpha-bungarotoxin with high affinity.