Effect of a single injection of reserpine on kinetics of 3H-dexamethasone binding to receptors of the cat hypothalamus and hippocampus.

Abstract

Cats were injected intraperitoneally with reserpine (5 mg/kg) or saline and sacrificed 16 h later. Hypothalamic and hippocampal cytosols were assayed for the kinetics of 3H-dexamethasone (3H-DM) binding. A parallel series was performed in which saline-injected cats were infused via venocatheter with hydrocortisone (HC). Reserpine-injected cats were infused with saline. The hypothalamic cytosol of reserpinized cats showed a marked decrease in 3H-DM binding capacity relative to that from saline-treated cats. Hippocampal cytosol 3H-DM binding capacity was unaffected by reserpinization. Infusion of high levels of HC reduced the amount of 3H-DM binding in the hypothalamus, but did not account for all the reduction found after reserpine treatment. HC infusion had no effect on hippocampal binding capacity. Reserpine treatment did not change the dissociation constant differences between the two brain regions. The data suggest that depletion of neurotransmitters by reserpine treatment from the hypothalamus, but not the hippocampus, significantly reduces the number of 3H-DM binding sites and that such a reduction is due, in part, to the effects of reserpine and not to high circulating levels of HC.