title: Forced swim stress: supersensitivity of the isolated rat pacemaker to the chronotropic effect of isoprenaline and the role of corticosterone.
abstract: 1. Forced swim (three daily sessions) resulted in an increased plasma corticosterone level and supersensitivity of the isolated rat pacemaker to the chronotropic effect of isoprenaline. 2. Bilateral adrenalectomy, performed 2 days before forced swim, abolished the development of pacemaker supersensitivity to isoprenaline. 3. Administration to rats of the antiglucorticoid compound RU-38486 prevented the development of pacemaker supersensitivity to isoprenaline. Pretreatment of rats not submitted to forced swim with the synthetic glucocorticoid RU-28362 causes pacemaker supersensitivity to isoprenaline. 4. Pretreatment of rats with diazepam or imipramine which block the forced swim-induced increase in the plasma level of corticosterone prevented the development of pacemaker supersensitivity to isoprenaline. 5. It is concluded that corticosterone plays a critical role in the modulation of the sensitivity to catecholamines of the pacemaker beta-adrenoceptors during adaptation to repeated stress.
authors.affiliation: Department of Physiology, School of Medicine, Pontificia Universidade Catolica de Campinas, Sao Paulo, Brazil.
authors.forename: M J
authors.initials: MJ
authors.lastname: Moura
authors.forename: S
authors.initials: S
authors.lastname: De Moraes
mesh_terms: D000311:Adrenal Glands / Q000502:physiology / Q000601:surgery; D000315:Adrenalectomy; D000818:Animals; D016280:Atrial Function, Right / Q000187:drug effects* / Q000502:physiology; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D003345:Corticosterone / Q000097:blood / Q000502:physiology*; D004347:Drug Interactions; D006339:Heart Rate / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D015735:Mifepristone / Q000494:pharmacology; D005082:Physical Exertion / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018343:Receptors, Adrenergic, beta-2 / Q000502:physiology; D012680:Sensitivity and Specificity; D013312:Stress, Physiological / Q000503:physiopathology*; D013550:Swimming / Q000502:physiology
chemical_list: D018343:Receptors, Adrenergic, beta-2; D015735:Mifepristone; D007545:Isoproterenol; D003345:Corticosterone