title: Glucocorticoid Fast Feedback Inhibition of Stress-Induced ACTH Secretion in the Male Rat: Rate Independence and Stress-State Resistance.
abstract: Normal glucocorticoid secretion is critical for physiological and mental health. Glucocorticoid secretion is dynamically regulated by glucocorticoid-negative feedback; however, the mechanisms of that feedback process are poorly understood. We assessed the temporal characteristics of glucocorticoid-negative feedback in vivo using a procedure for drug infusions and serial blood collection in unanesthetized rats that produced a minimal disruption of basal ACTH plasma levels. We compared the negative feedback effectiveness present when stress onset coincides with corticosterone's (CORT) rapidly rising phase (30 sec pretreatment), high plateau phase (15 min pretreatment), or restored basal phase (60 min pretreatment) as well as effectiveness when CORT infusion occurs after the onset of stress (5 min poststress onset). CORT treatment prior to stress onset acted remarkably fast (within 30 sec) to suppress stress-induced ACTH secretion. Furthermore, fast feedback induction did not require rapid increases in CORT at the time of stress onset (hormone rate independent), and those feedback actions were relatively long lasting (≥15 min). In contrast, CORT elevation after stress onset produced limited and delayed ACTH suppression (stress state resistance). There was a parallel stress-state resistance for CORT inhibition of stress-induced Crh heteronuclear RNA in the paraventricular nucleus but not Pomc heteronuclear RNA in the anterior pituitary. CORT treatment did not suppress stress-induced prolactin secretion, suggesting that CORT feedback is restricted to the control of hypothalamic-pituitary-adrenal axis elements of a stress response. These temporal, stress-state, and system-level features of in vivo CORT feedback provide an important physiological context for ex vivo studies of molecular and cellular mechanisms of CORT-negative feedback.
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309.
authors.forename: Chad D
authors.initials: CD
authors.lastname: Osterlund
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309.
authors.forename: Mariana
authors.initials: M
authors.lastname: Rodriguez-Santiago
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309.
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Woodruff
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Newsom
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309.
authors.forename: Anjali P
authors.initials: AP
authors.lastname: Chadayammuri
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Spencer
mesh_terms: D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D003345:Corticosterone / Q000494:pharmacology*; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D025461:Feedback, Physiological / Q000187:drug effects*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D013312:Stress, Physiological / Q000187:drug effects* / Q000502:physiology; D013315:Stress, Psychological / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone