Corticosterone exerts site-specific and state-dependent effects in prefrontal cortex and amygdala on regulation of adrenocorticotropic hormone, insulin and fat depots

Chronic stress stimulates corticosterone secretion and recruits brain pathways that regulate energy balance (caloric acquisition and deposition) and facilitate hypothalamic-pituitary-adrenal responsiveness to new stressors. We implanted corticosterone or cholesterol bilaterally either near the central nucleus of the amygdala (CeA) or in the prefrontal cortex to determine whether high concentrations of the steroid act at either site, with or without chronic stress. Rats were adrenalectomized and treated systemically with low doses of corticosterone. Half were maintained at room temperature and the other half were exposed to 5 degreesC cold for 5 days before all rats were restrained. There was limited diffusion of corticosterone from brain implants. Corticosterone in prefrontal cortex, but not CeA, decreased plasma insulin and adrenocorticotropic hormone (ACTH) responses to acute restraint in both control and chronically cold stressed rats. Corticosterone implants near CeA decreased the weight of fat depots only in cold; corticosterone implants in prefrontal cortex were ineffective. We conclude that (i) corticosterone inhibits insulin and ACTH secretion by an action in prefrontal cortex but not CeA; (ii) high concentrations of corticosterone secreted during chronic stress alter metabolism through (autonomic) outputs of the CeA and prefrontal cortex in site- and variable-specific fashion; and (iii) the amygdala is a component of a stress-recruited, state-dependent pathway.