[Application of group psychology of animals into pharmacological studies. 12. Specificities of actions of psychotropic drugs on emotional and exploratory behaviors of a single mouse or groups of 2 or 3 animals].

The exploratory movement recorder of Tokyo University of Education type was utilized to assess the exploratory motor activity of groups of 1, 2 and 3 mice of the dd-strain. As the animals were observed during 15 min periods to move spontaneously, psychotropic drugs were administered and the specific actions of these agents were determined. Each drug was given i.p. in a dose which proved non-effective in a single mouse. Observations were as follows: The ratio of exploratory motor activity of each pair of mice as compared to a single mouse was not always different from that of control animals. When a 3rd mouse was added to the pair, the motor activity either increased or decreased considerably. The rate of increase in motor activity was calculated 45 min after caffeine, pentetrazol, ephedrine and DL-amphetamine and was found to be less than in the control animals. After administration of chlordiazepoxide, diazepam, imipramine, chlorpromaxine or mescaline, the rate of increase in motor activity was considerably greater than in the controls. With dimorphoramine or hexobarbital, the rate was much the same as control. After beta-oxy gamma-aminobutyric acid, the rate was slightly increased and with diphenhydramine the rate was slightly less than control. Thus the exploratory motor activity of 3 mice as compared to that of 2, decreased considerably after administration of psychotropic stimulants, while after psychotropic depressants, an even greater increase was observed. We have already reported on the mutual relation of mice in fighting episodes and E1-mice convulsions. Those relations were, however, responses elicited by the physical stimulation. In contrast, the mutual relation in this paper is more of a natural nature. In view of observations in this paper, it is considered that CNS stimulants increase the mutual, emotional, checking behavior in groups of 3 animals while CNS depressants decrease the checking behavior. Such behavior is one example of the emotional conduct when a 3rd party is added to a 2 member group.