Influence of home-cage lighting conditions on shock-induced fighting.

Abstract

The influence of home-cage lighting conditions on shock-induced aggression in rats was studied. Rats were tested 6 times within 24 h and demonstrated that subjects maintained on a light/dark (LD) cycle fought more than rats maintained on a 24 h light schedule (LL). A periodic trend could be identified in the data of the LD groups but not in the data of the LL groups. Castration of adults did not influence the lighting effects, but castration of weanling rats eliminated the group difference between LL and LD groups. The LD rats castrated at weaning showed the periodic trend characteristic of all of the LD groups tested within 24 h. Time of testing was a significant variable in the LD groups but unimportant in the LL groups. The difference beween the LD and LL groups does not emerge in a daily testing procedure.