SORTING OUT ANTIAGGRESSIVE AND MOTOR EFFECTS OF HALOPERIDOL BY MEANS OF TOLERANCE DEVELOPMENT

The effects of haloperidol on agonistic behaviour of mice were studied in an attempt to find out if antiaggressive and motor actions of this drug could be dissociated by means of tolerance development. Agonisti c behaviour was studied in isolated male mice that confronted standard opponents (anosmic and grouped conspecifics) in a neutral area, The a ggressive and motor behaviours of the experimental animals were evalua ted 30 min or 24 h after a single injection i.p. of haloperidol (0.4 m g kg(-1)) or following the last of a series of 7 and 15 injections of the drug, When evaluated 30 min after the last injection, a clear diss ociation between antiaggressive and motor effects was observed after h aloperidol administration: tolerance to the motor effects developed wi th repeated injections, and no tolerance to the antiaggressive effects was evident. No residual effects were found at 24 h. The results sugg est that antiaggressive and motor actions of the drug are mediated thr ough different neurophysiological mechanisms.