THE INTEGRITY OF THE SOCIAL HIERARCHY IN MICE FOLLOWING ADMINISTRATION OF PSYCHOTROPIC DRUGS

Mice living in small groups form a rigid, despotic social hierarchy that resists change even when psychotropic drugs are administered, making rapid pharmacological shifts in social rank impossible. Maintaining territory and social interaction are key to this inertia. Drugs such as diazepam, droperidol, and mescaline alter these factors to different degrees and vary in their ability to preserve hierarchy stability. Lowering aggression in a subordinate mouse does not change its social position. However, chronic administration of these drugs can eventually invert the hierarchy when a competitive rival is present, with the speed of inversion depending on the existing hierarchy type. The drugs' capacity to maintain hierarchy inertia may serve as an index of their effect on species-specific behaviors, particularly aggression.

Study at a glance

Abstract

Mice in small groups develop a despotic type of social hierarchy, a feature of which is to resist alteration through the medium of psychotropic drugs. This makes a rapid pharmacologically induced change in the social hierarchy impossible. Patrolling the territory and a certain level of social interaction are both critical factors in maintaining the phenomenon of inertia in the social hierarchy. Psychotropic drugs (diazepam, droperidol and mescaline) altered both these factors to a varying degree and also displayed a differing ability to maintain the inertia of the social hierarchy. A drug‐induced alteration in the level of aggression in a subordinate mouse in a group of three does not cause an alteration in its social position. Chronic administration of diazepam, droperidol or mescaline, all of which alter the level of aggression in different ways, can result in an inversion of the social hierarchy where a competitive rival is present in the group of mice. The rate of inversion of the social hierarachy depends on the type of pre‐existing social hierarchy. It is suggested that the ability of psychotropic drugs to maintain the inertia of the hierarchy be used as an index of their effect upon certain types of species‐specific behaviour; in particular aggression.