Pharmacology Biochernixtry & Behavior, Vol. 13, pp. 287-290. Printedin the U.S.A. An Automated Device for Screening the Effects of Psychotropic Drugs on Aggression and Motor Activity in Mice STEFANO PUGLISI-ALLEGRA AND PAOLO RENZI istituto di Psicobiologia e Psicofarmacologia, CNR via Reno, I---00198 Roma. Italy Received 1 January 1980 PUGLISI-ALLEGRA, S. AND P. RENZI. An automated device fi~r screening the e lfects of psychotropic drugs on aggres~'ion and motor activity in mice. PHARMAC. BIOCHEM. BEHAV. 13(2) 287-290, 1980.--An automated technique for measuring simultaneously aggressive behavior and motor activity in mice is described. This technique "allowsmeasure of aggressive behavior and motor activity continuously throughout long-lasting periods without disturbing the animals except for feeding, watering and cleaning the cages. The effects of n-D-propylacetate, a drug which "affects aggression without affecting motor activity, were also tested. Aggression Motor activity Psychotropic drugs Mice Method n-D-propylacetate A DEVICE to detect and quantify fighting episodes and, at the same time--but in independent fashion--, general activ- ity in groups of two or more mice is described. The apparatus was designed starting from the observation that general ac- tivity and fighting episodes of animals living in a breeding cage produce vibrations of different intensities on the floor of the cage. In particular, the collisions determined by the bodies, the legs and the tails against the floor during fighting produce vibrations that are the most intense among those produced by animals living in breeding conditions. Thus, such an apparatus should detect and discriminate different kinds of activity corresponding either to aggressive behavior or to non-aggressive motor activity. APPARATUS ( "OtHponcI1L~ The major components of the apparatus are the experi- mental cage and the processing unit. The experimental cage is a modified breeding cage in which the floor is replaced by a zincate mesh (weighing 1200 g/m e and with squares of 8 mm side) fixed to the walls at 4 cm from the tray which collects the excrements. The mesh is fixed by means of screws to four Plexiglas blocks glued to the walls of the cage. The distance between the lid and the floor of the cage is 6.5 cm. The mesh collects the vibrations produced by the animals" activity and transmits them to 4 dynamic microphones placed at the corners of the cage. Each microphone is fitted in a rubber capsule and plugged to the mesh (Fig. I). This plugging allows removal of the microphones in order to clean the cage. The microphones are connected in series to obtain an improvement of sensibility throughout the mesh. Microphone signals are processed by the circuit shown in Fig. 2. The processing unit consists of two amplifiers so that one channel will detect both low and high intensity noises (referred to as "total motor activity") independently of the other channel which will detect only high intensity noises corresponding to fighting behavior (referred to as "fighting motor activity"). The evaluation of motor activity without fighting activity (referred to as "general motor activity") is obtained by subtracting activity scores concerning "'fighting motor activity" from activity scores concerning "total motor activity". Related Equipment A Grason Stadler Programmer was used for more detailed information on different aggressive patterns such as latency to the first fight, number and time of fighting episodes. Feeding behavior is a kind of activity that will be recorded only if the lid--where the food container is located--is fixed to the cage; therefore it is possible to avoid recording of this activity by fixing the lid to supports that are not in contact with the experimental cage. Furthermore, it must be pointed out that activity and fighting produce through the mesh noises differing only in intensity, not in frequency distribution. Thus, differences in the type of mesh or in the connections of the mesh to the cage do not affect discrimination between the two levels of noise. Finally, to avoid the interference of extermd noise each microphone can be covered with polyurethane foam and the entire apparatus can be placed in a sound-insulated cubicle. SUPPORTING DATA Animals Male mice of the DBA/2 strain were used. The mice were randomly assigned to two housing conditions, either individ- ually housed (isolated) for 8 weeks or in groups of 6 animals Copyright ~ 1980 ANKHO International Inc.--0091-3057/80/080287-04500.90/0