Individual motor activity--relationships to dopaminergic responses.

Owing to motor activity mice were divided into two groups in a running-wheel test: low-active mice (LAM) and high-active mice (HAM). Locomotor activities in the running wheel and in glass boxes are compared. The HAM showed a more intensive explorative behavior than LAM and were also more responsive in terms of exogenous factors than LAM. In contrast, LAM showed higher locomotor activity than HAM after habituation. Analyzing the response of LAM and HAM to dopaminergic agonists such as apomorphine, bromocriptine, and amphetamine, the role of specific dopaminergic mechanisms for the two types is discussed. Although apomorphine mainly stimulated the climbing activity in HAM, bromocriptine (climbing activity) and amphetamine (locomotion) had stronger effects in LAM. Differences may be assumed between LAM and HAM concerning the nigrostriatal and/or mesolimbic dopaminergic mechanisms. On the one hand, climbing activity following apomorphine application accompanied by stereotypes may suggest a stronger activation of striatal dopaminergic mechanisms in HAM. On the other hand, climbing activity following bromocriptine accompanied by jumping behavior, as well as the stimulation of locomotion after amphetamine, suggests a more effective activation of mesolimbic dopaminergic structures in LAM.