Invited Symposium: Behaviour-Induced Neural Events after Brain Injury
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Tillerson, J (Department of Psychology, University of Texas at Austin, USA)
Humm, JL (Department of Psychology, University of Texas at Austin, USA)
Morin, S (Department of Psychology, University of Texas at Austin, USA)
Aronowski, J (Department of Neurology, University of Texas Health Sciences at Houston, USA)
Grotta, J (Department of Neurology, University of Texas Health Sciences at Houston, USA)
Schallert, T (Department of Psychology & Institute for Neuroscience, University of Texas at Austin, USA)
Abstract
Extreme forced overuse of the affected forelimb during an early critical period results in exaggeration of the original damage following focal unilateral electrolytic lesions (Kozlowski et al., 1996) and fluid percussion injury (Kozlowski et al., 1997) of the sensorimotor cortex. In the current studies, we examined the effects of forced overuse of the affected forelimb in a unilateral focal ischemic stroke model and in a unilateral 6-OHDA model of Parkinson's disease using anatomical, neurochemical and behavioral outcome tests. Male Long-Evans rats were used. Unilateral cerebral ischemia was induced using tandem MCA/CCA occlusion for 90 minutes, a paradigm that has been shown to result in minimal to no neuronal damage. Immediately following reperfusion, the ipsilateral limb was immobilized in a one-sleeved plaster of Paris cast, or the animal was left uncasted, for 3 or 14 days. TTC staining revealed an increase in infarct volume in casted rats. Plaster of paris casts were also used to restrict use of the nonimpaired forelimb for 1 week after unilateral 6-OHDA infusion (10 micrograms into the nigrostriatal tract). Uncasted animals failed to recover when tested up to 60 days after 6-OHDA treatment, and displayed apomorphine-induced contralateral rotation indicating severe dopamine depletion. In contrast, casted rats, like controls, displayed no detectable impairment or asymmetry of limb use, could use the contralateral forelimb for vertical and lateral weight shifting, and showed no contralateral turning to apomorphine. These results suggest that forced motor rehabilitation of the affected forelimb during or soon after degeneration may be beneficial following unilateral DA depletion, but may be detrimental following ischemic injury.
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Presentation Number SAbland0844
Keywords: ischemia, 6-OHDA, use-dependent, forelimb use, rehabilitation
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