Abstract
Stress responses studied earlier in Norway rats (Rattus norvegicus) selected for the absence or enhancement of the aggressive–fearful attitude to humans (tame and aggressive behavior, respectively) were targeted mainly at nonsocial factors, whereas the data on the consequences of social stress induced, in particular, by interactions with a conspecific are scarce. It has already been shown that the selection of Norway rats for tame and aggressive behavior towards humans causes an attenuation or enhancement of intraspecific intermale aggression. In order to find out whether the differences in aggressiveness are accompanied by hormonal changes, variations of the blood levels of corticosterone and testosterone after the test for intermale aggression have been studied in tame, aggressive, and unselected rats reproduced in a vivarium for 7–8 generations as a reference. The goal of this work is to investigate the effect of selection for attitude to humans on agonistic interactions in an unfamiliar cage or in neutral territory and on the subsequent variation of blood corticosterone and testosterone levels in tame, aggressive, and unselected rats. In our experiments, tame males show longer attack latency than aggressive or unselected ones, and the duration of their aggressive behavior and the number of its patterns are much less, close to zero. In the test in neutral territory, aggressive rats are inferior to unselected in the overall time of confrontations. More pronounces signs of aggressiveness in unselected males in comparison to aggressive or tame are noted against the background of elevated basal corticosterone levels and elevated stress responsiveness. The lower aggressiveness of tame rats in the test in neutral territory correlates with the lower testosterone level after the test as compared to unselected or aggressive animals.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
