title: Hypothermia after chronic mild stress exposure in rats with a history of postnatal maternal separations.
abstract: The circadian system develops and changes in a gradual and programmed process over the lifespan. Early in life, maternal care represents an important zeitgeber and thus contributes to the development of circadian rhythmicity. Exposure to early life stress may affect circadian processes and induce a latent circadian disturbance evident after exposure to later life stress. Disturbance of the normal regulation of circadian rhythmicity is surmised to be an etiological factor in depression. We used postnatal maternal separation in rats to investigate how the early life environment might modify the circadian response to later life unpredictable and chronic stress. During postnatal days 2-14, male Wistar rats (n = 8 per group) were daily separated from their mothers for a period of either 180 min (long maternal separation; LMS) or 10 min (brief maternal separation; BMS). In adulthood, rats were exposed to chronic mild stress (CMS) for 4 weeks. Body temperature, locomotor activity and heart rate were measured and compared before and after CMS exposure. LMS offspring showed a delayed body temperature acrophase compared to BMS offspring. Otherwise, adult LMS and BMS offspring demonstrated similar diurnal rhythms of body temperature, locomotor activity and heart rate. Exposure to CMS provoked a stronger and longer lasting hypothermia in LMS rats than in BMS rats. The thermoregulatory response appears to be moderated by maternal care following reunion, an observation made in the LMS group only. The results show that early life stress (LMS) in an early developmental stage induced a thermoregulatory disturbance evident upon exposure to unpredictable adult life stressors.
authors.affiliation: Department of Biological and Medical Psychology, University of Bergen , Bergen , Norway .
authors.forename: Jelena
authors.initials: J
authors.lastname: Mrdalj
authors.forename: Ase
authors.initials: A
authors.lastname: Lundegaard Mattson
authors.forename: Robert
authors.initials: R
authors.lastname: Murison
authors.forename: Finn
authors.initials: F
authors.lastname: Konow Jellestad
authors.forename: Anne Marita
authors.initials: AM
authors.lastname: Milde
authors.forename: Ståle
authors.initials: S
authors.lastname: Pallesen
authors.forename: Reidun
authors.initials: R
authors.lastname: Ursin
authors.forename: Bjørn
authors.initials: B
authors.lastname: Bjorvatn
authors.forename: Janne
authors.initials: J
authors.lastname: Grønli
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001010:Anxiety, Separation / Q000097:blood / Q000150:complications* / Q000503:physiopathology / Q000523:psychology; D001522:Behavior, Animal; D015415:Biomarkers / Q000097:blood; D001833:Body Temperature Regulation; D002908:Chronic Disease; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood; D004195:Disease Models, Animal; D005260:Female; D006339:Heart Rate; D007035:Hypothermia / Q000097:blood / Q000209:etiology* / Q000503:physiopathology / Q000523:psychology; D008297:Male; D008426:Maternal Deprivation; D009043:Motor Activity; D017208:Rats, Wistar; D012307:Risk Factors; D013315:Stress, Psychological / Q000097:blood / Q000150:complications* / Q000503:physiopathology / Q000523:psychology; D013997:Time Factors
chemical_list: D015415:Biomarkers; D003345:Corticosterone