title: Sustained release of corticosterone in rats affects reactivity, but does not affect habituation to immobilization and acoustic stimuli.
abstract: Depression is often preceded by stressful life events and accompanied with elevated cortisol levels and glucocorticoid resistance. It has been suggested that a major depressive disorder may result from impaired coping with and adaptation to stress. The question is whether or not hypothalamus-pituitary-adrenal (HPA)-axis dysfunction influences the process of adaptation. We examined the effect of a dysregulated HPA-axis on the adaptation to acoustic stimuli in rats with or without preceding restraint stress. HPA-axis function was altered via slow release of corticosterone (CORT, 90 mg) from subcutaneously implanted pellets for 7 or 14 days. The rate of body temperature increases during restraint (10 min) and the response to acoustic stimuli (of 80+120 dB) were used to quantify daily stress reactivity. Rats habituated to either stress regardless of CORT treatment. CORT treatment combined with restraint decreased the initial reactivity and the variability in response, but the rate of habituation was not influenced. These results show that suppressing normal HPA-axis function by chronic exposure to CORT does affect the course of habituation, but not habituation per se. This implies that altered HPA-axis function in depressed patients may not be causally related to stress coping, but instead may influence the course of the disorder.
authors.affiliation: Graduate School of Behavioral and Cognitive Neuroscience, University of Groningen, University Center of Psychiatry, University Medical Center Groningen, The Netherlands. m.a.c.tanke@med.umcg.nl
authors.forename: Marit A C
authors.initials: MA
authors.lastname: Tanke
authors.forename: Dirk S
authors.initials: DS
authors.lastname: Fokkema
authors.forename: Bennard
authors.initials: B
authors.lastname: Doornbos
authors.forename: Folkert
authors.initials: F
authors.lastname: Postema
authors.forename: Jakob
authors.initials: J
authors.lastname: Korf
mesh_terms: D000161:Acoustic Stimulation; D000208:Acute Disease; D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D001831:Body Temperature; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002908:Chronic Disease; D003345:Corticosterone / Q000008:administration & dosage / Q000494:pharmacology*; D003692:Delayed-Action Preparations; D004435:Eating / Q000187:drug effects / Q000502:physiology; D006185:Habituation, Psychophysiologic / Q000187:drug effects / Q000502:physiology*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D008297:Male; D009929:Organ Size / Q000187:drug effects / Q000502:physiology; D010913:Pituitary-Adrenal System / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology*; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology
chemical_list: D003692:Delayed-Action Preparations; D003345:Corticosterone