The Journal of Neuroscience, January 15, 2003, 23(2):579-586
A Novel Skilled-Reaching Impairment in Paw Supination on the
"Good" Side of the Hemi-Parkinson Rat Improved with
Rehabilitation
Patricia
Vergara-Aragon1,
Claudia L. R.
Gonzalez2, and
Ian Q.
Whishaw1
1 The Canadian Centre for Behavioural Neuroscience,
University of Lethbridge, Lethbridge, Alberta, Canada, T1K 3M4, and
2 Departamento de Fisiologia, Facultad de Medicina
Universidad Nacional Autonoma de Mexico, Mexico, D.F. CP 07010
Parkinson's disease is characterized by tremor, rigidity,
bradykinesia, and postural abnormalities ascribed to the loss of nigrostriatal dopamine (DA). Symptoms similar to the human condition can be produced in the rat by DA-depleting 6-hydroxydopamine
injections made into the nigrostriatal system. After a unilateral
lesion, the rat symptoms include sensory and motor impairments and
turning biases reflecting motor abnormalities to the
contralateral-to-depletion side of the body. In addition, a number of
studies on skilled reaching report impairments in the use of the
ipsilateral limb. It is suggested that the ipsilateral deficit is
secondary to the contralateral motor impairments however. Here we
re-examine how rats with unilateral DA depletion use their ipsilateral
limb for skilled reaching for food. We provide the first description of an impairment on the ipsilateral-to-depletion side of the body of the
rat and the first demonstration of amelioration of the defect using
behavioral therapy. Video analysis of rats reaching for single pellets
of food with the ipsilateral limb revealed that, although limb
advancement and food grasping were normal, paw supination and food
release to the mouth were impaired. Consequently, the animals were
unable to transport a grasped food pellet to the mouth. Behavioral
therapy, consisting of training in a simpler reaching task, strikingly
lessened the impairment and improved reaching movements to the point
that the rats could transport the food to the mouth. The results are
discussed in relation to possible causes of the ipsilateral impairment,
its treatment, and to relevant research on human Parkinson patients,
indicating that they display bilateral improvements after unilateral treatments.
Key words:
dopamine depletion; dopamine and skilled movement; 6-hydroxydopamine; nigrostriatal lesion; Parkinson analog rat; Parkinson's disease; Parkinson's disease rat model; skilled reaching; Parkinson's therapy; rehabilitation and Parkinson's disease
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