Differentiation of motor inactivation from movement asymmetry effects in an animal model of hemi-parkinsonism.

Rats subjected to unilateral 6-hydroxydopamine lesion of the pars compacta of the substantia nigra sustained a wide range of dopamine (DA) loss in the neostriatum. Residual DA levels of < 50% resulted in behavioural impairments which correlated with the degree of DA denervation, whereas no such effects occurred with residual DA levels of > 50%. Within 1 week after surgery the effects of the lesion on motor activation recovered whereas movement asymmetrics exhibited no recovery. In addition, movement asymmetry effects were not correlated with motoric inactivation effects. This finding indicates that dopamine denervation of the neostriatum disrupts sensory/motor integration and attentional processes rather than motor activation.