Motivational versus motor impairment after haloperidol injection or 6-OHDA lesions in the ventral tegmental area or substantia nigra in rats.

The effects of blockade of dopaminergic receptors as well as the lesions of dopaminergic neurons on the behaviour of rats in "motivational" and "motor" tests were examined. Both systemic injection of haloperidol and 6-OHDA lesions in the ventral tegmental area (VTA) or substantia nigra, pars compacta (SN/pC) induced a decrease in the number of wins made by thirsty animals fighting for water in a water competition test. The rats with lesions in the VTA became insensitive to motivational thirst stimuli. The reaction of rats lesioned in the SN/pC was still dependent on the level of thirst. Both groups did not differ from controls in the amount of water intake. In the rotating rod test the animals with destroyed nigrostriatal system showed a substantial motor impairment, while destruction of the mesolimbic system had no effect in that test. The role of dopaminergic systems in terms of their involvement in the control of motivational arousal and motor performance has been discussed.