Alterations in core body temperature, locomotor activity, and corticosterone following acute and repeated social defeat of male NMRI mice

Repeated social defeat of male NMRI mice, coupled with the stress of contin uously living opposite a dominant animal, induces a citalopram-reversible i ncrease in anxiety. The experiments reported in the present paper were perf ormed in an attempt to further validate this paradigm by studying the effec ts of acute and repeated social defeat on corticosterone and the circadian rhythms of core body temperature and locomotor activity, measured by teleme try. Acute social defeat induced a large (controls: 37.14 +/- 0.29 degreesC ; subordinates: 39.79 +/- 0.33 degreesC) increase in core body temperature and corticosterone (controls: 30.14 +/- 2.70 ng/ml; subordinates: 89.62 +/- 9.25 ng/ml). Repeated social defeat (24 defeats) induced a chronic elevati on in core body temperature across 24-h (controls: 36.62 +/- 0.04 degreesC; subordinates: 37.11 +/- 0.16 degreesC) in subordinate animals and a very l arge increase in corticosterone (controls: 28.60 +/- 1.27 ng/ml; subordinat es: 441.52 +/- 8.86 ng/ml). These results illustrate that the chronic socia l defeat procedure described in this paper induces a state of chronic stres s in the subordinate animals. Further studies are warranted to ascertain if the chronic hyperthermia and increases in corticosterone observed in the s ubordinate animals could be attenuated by chronic antidepressant treatment, thus further extending the predictive validity of this model. (C) 2001 Els evier Science Inc. All rights reserved.