CAPACITY OF CORTICOSTERONE RECEPTOR SYSTEM IN RAT BRAIN: CONTROL BY NEUROPEPTIDES AND HORMONES

Abstract

This chapter describes that hippocampal corticosterone receptor capacity increases after removal of the pituitary and is decreased in rats homozygous for diabetes insipidus. Replacement therapy with various hormones and neuropeptides showed that the homologous hormone , thyroxine and testosterone and peptides related to vasopressin and adrenocorticotropic hormone (ACTH) all are involved in the control of hippocampal corticosterone receptor capacity. Changes in steroid receptor capacity have been correlated functionally with modulation of the sensitivity of target cells to these steroids. The chapter describes attempts to alter the amount of receptor sites for corticosterone in the hippocampus to define further the role of these receptors in control of adaptive behavior. Determination of the apparent maximal binding capacity of the hippocampal corticosterone receptor system was achieved in vitro in cytosol, using 3 H-corticosterone concentrations ranging from 0.5-50 nM. Bilateral adrenalectomy was performed 24 hours prior to sacrifice. Replacement therapy and hormone administration were discontinued 24 hours before sacrifice of the animals.