title: Adaptation of the hypothalamus-pituitary-adrenal axis to daily repeated stress does not follow the rules of habituation: A new perspective.
abstract: Repeated exposure to a wide range of stressors differing in nature and intensity results in a reduced response of prototypical stress markers (i.e. plasma levels of ACTH and adrenaline) after an acute challenge with the same (homotypic) stressor. This reduction has been considered to be a habituation-like phenomenon. However, direct experimental evidence for this assumption is scarce. In the present work we demonstrate in adult male rats that adaptation of the hypothalamus-pituitary-adrenal (HPA) axis to repeated stress does not follow some of the critical rules of habituation. Briefly, adaptation was stronger and faster with more severe stressors, maximally observed even with a single exposure to severe stressors, extremely long-lasting, negatively related to the interval between the exposures and positively related to the length of daily exposure. We offer a new theoretical view to explain adaptation to daily repeated stress.
authors.affiliation: Institut de Neurociències and Unitat de Fisiologia Animal (Facultat de Biociències), Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193, Spain; Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Rabasa
authors.affiliation: Institut de Neurociències and Unitat de Fisiologia Animal (Facultat de Biociències), Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193, Spain; Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Madrid, Spain.
authors.forename: Humberto
authors.initials: H
authors.lastname: Gagliano
authors.affiliation: Institut de Neurociències and Unitat de Fisiologia Animal (Facultat de Biociències), Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193, Spain; Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Madrid, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Pastor-Ciurana
authors.affiliation: Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Madrid, Spain; Institut de Neurociències and Unitat Psicobiologia (Facultat de Psicologia), Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Fuentes
authors.affiliation: Institut de Neurociències and Unitat de Fisiologia Animal (Facultat de Biociències), Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193, Spain; Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Madrid, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Belda
authors.affiliation: Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Madrid, Spain; Institut de Neurociències and Unitat Psicobiologia (Facultat de Psicologia), Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain.
authors.forename: Roser
authors.initials: R
authors.lastname: Nadal
authors.affiliation: Institut de Neurociències and Unitat de Fisiologia Animal (Facultat de Biociències), Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193, Spain; Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Madrid, Spain. Electronic address: antonio.armario@uab.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: Armario
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D006185:Habituation, Psychophysiologic; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology*; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D013315:Stress, Psychological / Q000473:pathology / Q000503:physiopathology / Q000523:psychology
keywords: ACTH; Corticosterone; Habituation; Immobilization; Repeated stress; Restraint; Water stress; c-fos