title: Forced swimming-induced oxytocin release into blood and brain: Effects of adrenalectomy and corticosterone treatment.
abstract: The oxytocin (OXT) system is functionally linked to the HPA axis in a reciprocal and complex manner. Certain stressors are known to cause the simultaneous release of OXT and adrenocorticotrophic hormone (ACTH) followed by corticosterone (CORT). Furthermore, brain OXT attenuates ACTH and CORT responses. Although there are some indications of CORT influencing OXT neurotransmission, specific effects of CORT on neurohypophyseal or intra-hypothalamic release of OXT have not been studied in detail. In the present set of experiments, adult male rats were adrenalectomized (ADX) or sham-operated and fitted with a jugular vein catheter and/or microdialysis probe targeting the hypothalamic paraventricular nucleus (PVN). Blood samples and dialysates were collected before and after forced swimming (FS) and analyzed for CORT, ACTH and AVP concentrations (in plasma) and OXT concentrations (in plasma and dialysates). Experimental treatments included acute infusion of CORT (70 or 175μg/kg i.v.) 5min prior to FS, or subcutaneous placement of 40% CORT pellets resulting in stable CORT levels in the normal basal range. Although ADX did not alter basal OXT concentrations either in plasma or in microdialysates from the PVN, it did cause an exaggerated peripheral secretion of OXT and a blunted intra-PVN release of OXT in response to FS. CORT pellets did not influence either of these ADX-induced effects, while acute infusion of 175μg/kg CORT rescued the stress-induced rise in OXT release within the PVN and modestly increased peripheral OXT secretion. In conclusion, these results indicate that CORT regulates both peripheral and intracerebral OXT release, but in an independent manner. Whereas the peripheral secretion of OXT occurs simultaneously to HPA axis activation in response to FS and is modestly influenced by CORT, HPA axis activation and circulating CORT strongly contribute to the stress-induced stimulation of OXT release within the PVN.
authors.affiliation: Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Morelia, Mexico; Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: Luz
authors.initials: L
authors.lastname: Torner
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, USA.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Plotsky
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany; Department of Behavioural and Molecular Neurobiology, University of Regensburg, Regensburg, Germany. Electronic address: inga.neumann@ur.de.
authors.forename: Inga D
authors.initials: ID
authors.lastname: Neumann
authors.affiliation: Department of Behavioural and Molecular Neurobiology, University of Regensburg, Regensburg, Germany.
authors.forename: Trynke R
authors.initials: TR
authors.lastname: de Jong
mesh_terms: D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D003345:Corticosterone / Q000097:blood / Q000494:pharmacology; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010121:Oxytocin / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013312:Stress, Physiological / Q000502:physiology*; D013550:Swimming
chemical_list: D001127:Arginine Vasopressin; D010121:Oxytocin; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone
keywords: ACTH; Adrenalectomy; Corticosterone; HPA axis; Oxytocin; Stress