Individual differences in plasma catecholamine and corticosterone stress responses of wild-type rats: relationship with aggression.
Plasma noradrenaline (NA), adrenaline (A), and corticosterone (CS) responses to social and nonsocial stressors were studied in male members of a strain of wild-type rats, widely differing in their level of aggression. The aggressiveness was preliminarily established by measuring the latency time to attack (ALT) a male intruder in a standard resident-intruder test. Animals were then provided with a jugular vein cannula for blood sampling during stress exposure. Implanted rats were randomly assigned to 3 experimental treatments: social stress (defeat experience, SD), nonsocial stress (presentation of a shock-prod, SP) and control (animals undisturbed in their home cages, CTR). A significant correlation was found between ALT and the amount of time spent in burying the probe in SP rats: the more aggressive the animal, the higher the rate of burying behavior. SD induced a much stronger effect on plasma NA, A, and CS concentrations than SP. A significant negative correlation was found between ALT scores and values of the area under the response time curve for NA and A, in both SD and SP situations: the more aggressive the animal, the higher the catecholaminergic reactivity to the stressors. On the contrary, no evidence of a correlation between aggressiveness and plasma corticosterone responses was found, neither in SD nor in SP rats. These findings in an unselected strain of wild-type rats confirmed that an aggressive/active coping strategy is associated with a high sympathetic-adrenomedullary activation and support the concept of individual differentiation in coping styles as a coherent set of behavioral and neuroendocrine characteristics.
Sgoifo
A
A
Department of Animal Physiology, University of Groningen, Haren, The Netherlands. sgoifo@prfsio.bio.unipr.it
de Boer
S F
SF
Haller
J
J
Koolhaas
J M
JM
D000374:Aggression / Q000523:psychology*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D003345:Corticosterone / Q000378:metabolism*; D004837:Epinephrine / Q000378:metabolism; D008297:Male; D051381:Rats; D011930:Reaction Time / Q000502:physiology*; D013312:Stress, Physiological / Q000378:metabolism*
D002395:Catecholamines; D003345:Corticosterone; D004837:Epinephrine