An evaluation of the young dopamine-lesioned rat as an animal model for minimal brain dysfunction (MBD).

Three main symptoms of minimal brain dysfunction (MBD), a common disorder in children, are hyperactivity, learning disabilities, and attention deficits. Drugs like amphetamine and methylphenidate have been demonstrated to produce a significant behavioral improvement in these children. The behavioral response of young rats (3--4 weeks), with selective lesioning of the central dopaminergic system, to a novel environment was analyzed. Both the frequencies and durations of eight mutually exclusive and complementary behavioral categories were scored. By analyzing the behavior in this way it appeared that considerable hyperactivity and learning disabilities could be demonstrated in these rats. Moreover, the bout length of some behavioral categories was somewhat shortened, which might be an indication of deficits in attention. However, treatment of the animals with amphetamine did not produce any "therapeutic" effect on the three symptoms. Since pharmacotherapeutic support is, in our opinion, a "conditio sine qua non" for the validity of the model, we do not believe that the young DA-lesioned rat is an appropriate animal model for MBD.