Differential effects of ethyl (R,S)-nipecotate on the behaviors of highly and minimally aggressive female golden hamsters.

The GABA uptake inhibitor ethyl (R,S)-nipecotate produces a dose-dependent suppression of aggression in highly aggressive hamsters but not in minimally aggressive ones. This suppression occurs at doses below those producing peripheral cholinergic effects; at the highest dose used it persists after these effects have dissipated. Doses sufficient to suppress aggression have no significant effect on grooming, locomotor activity and other behaviors but do affect sunflower seed acceptance. The differential effects of the drug on highly and minimally aggressive animals may indicate that their differences in aggression are due to differences in endogenous GABAergic activity. These results, together with previous evidence for parallel circadian variation in GABA uptake and aggressive behavior, suggest that GABA uptake may be an important endogenous regulator of aggression.