Targeted motor rehabilitation dissociates corticobulbar versus corticospinal dysfunction in an animal model of Parkinson's disease.

Background: Recent evidence suggests that motor training may be beneficial for slowing the onset of motor impairments in Parkinson's disease (PD).

Objective: To examine the impact of targeted rehabilitation on limb motor and cranial motor function and the corresponding corticospinal and corticobulbar circuits in a rodent model of PD.

Methods: Baseline performance of limb (reaching) and cranial (licking) motor function were established prior to and 6 weeks following unilateral intrastriatal 6-hydroxydopamine (6-OHDA) infusions.

Differential sensitivity of cranial and limb motor function to nigrostriatal dopamine depletion.

The present study determined the differential effects of unilateral striatal dopamine depletion on cranial motor versus limb motor function. Forty male Long Evans rats were first trained on a comprehensive motor testing battery that dissociated cranial versus limb motor function and included: cylinder forepaw placement, single pellet reaching, vermicelli pasta handling; sunflower seed opening, pasta biting acoustics, and a licking task. Following baseline testing, animals were randomized to either a 6-hydroxydopamine (6-OHDA) (n=20) or control (n=20) group.

Striatal dopamine depletion induces forelimb motor impairments and disrupts forelimb movement representations within the motor cortex.

While limb motor deficits of Parkinson's disease are well characterized, the effects of striatal dopamine depletion on the motor cortex is poorly understood. We therefore aimed to 1) examine the effects of striatal dopamine depletion on forelimb function and cortical motor map topography and 2) explore potential relationships between forelimb function and cortical movement representations in an animal model of PD. Twenty-four male Long Evans rats were randomized to control or 6-hydroxydopamine (6-OHDA) groups.