Mechanisms underlying the increased plasma ACTH levels in chronic psychosocially stressed male mice

• Published in: PloS one Vol. 8; no. 12; p. e84161
• Main Authors: Füchsl, Andrea M, Langgartner, Dominik, Reber, Stefan O
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 23-12-2013; Public Library of Science (PLoS)
• Subjects: Adaptation; Adaptation, Physiological; Adrenal glands; Adrenocorticotropic hormone; Adrenocorticotropic Hormone - blood; Animals; Argipressin; Brain; Comparative analysis; Corticosterone; Corticotropin; Corticotropin-releasing hormone; Dexamethasone; Endocrinology; Feedback; Feedback inhibition; Feedback, Physiological; Gene Expression Regulation; Glands; Glucocorticoids; Housing; Hyperactivity; Hypothalamo-Hypophyseal System - physiology; Hypothalamus; Hypotheses; Laboratories; Male; Melanocyte stimulating hormone; Mice; Mice, Inbred C57BL; Negative feedback; Neurobiology; Neurohormones; Neurons - cytology; Neurosciences; Organ Size; Paraventricular Hypothalamic Nucleus - cytology; Pituitary; Pituitary (anterior); Pituitary gland; Pituitary-Adrenal System - physiology; Plasma; Proopiomelanocortin; Protein binding; Protein expression; Proteins; Psychiatry; Psychosis; Psychosomatic medicine; Psychotherapy; Psychotropic drugs; Receptors, Corticotropin-Releasing Hormone - metabolism; Receptors, Glucocorticoid - metabolism; Receptors, Mineralocorticoid - metabolism; Rodents; Secretion; Shc protein; Social interactions; Stress; Stress response; Stress, Physiological; Tacrolimus; Tacrolimus Binding Proteins - metabolism; Tacrolimus-binding protein; Time Factors; Vasopressin; Vasopressins - metabolism; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0084161

Mice exposed to chronic subordinate colony housing (CSC, 19 days), an established paradigm for chronic psychosocial stress, show unaffected basal morning plasma corticosterone (CORT) concentrations, despite enlarged adrenal glands and an increased CORT response to an acute heterotypic stressor. In the present study we investigate the mechanisms underlying these phenomena at the level of the pituitary. We show that both basal and acute stressor-induced (forced swim (FS), 6 min) plasma adrenocorticotropic hormone (ACTH) concentrations, the number of total and corticotroph pituitary cells, and relative protein expression of pituitary mineralocorticoid receptor and FK506-binding protein 51 was increased in CSC compared with single-housed control (SHC) mice, while relative corticotropin releasing hormone (CRH) receptor 1 (CRH-R1) and glucocorticoid receptor protein expression was down-regulated. Relative pituitary pro-opiomelanocortin and arginine vasopressin (AVP) receptor 1b (AVPR-1b) protein expression, FS (6 min)-induced ACTH secretion in dexamethasone-blocked mice, and the number of AVP positive magnocellular and parvocellular neurons in the paraventricular hypothalamic nucleus (PVN) was unaffected following CSC. Taken together, the data of the present study indicate that 19 days of CSC result in pituitary hyperactivity, under both basal and acute heterotypic stress conditions. Although further studies have to assess this in detail, an increased number of pituitary corticotrophs together with unaffected relative pituitary AVPR-1b and decreased CRH-R1 protein expression following CSC suggests that pituitary hyperdrive is mediated by newly formed corticotrophs that are more sensitive to AVP than CRH. Moreover, our data indicate that changes in PVN AVP and negative feedback inhibition seem not to play a major role in pituitary hyperactivity following CSC.