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Abstract
The nigrostriatal degeneration underlying Parkinson's disease (PD) is commonly modeled
in experimental animals by injection of the neurotoxin 6-hydroxydopamine (6-OHDA).
Although a wide variety of simple behavioural screens exist to assess the impact of
such dopamine lesions, more complex tasks that assess multiple parameters of an animal's
performance may provide a more sensitive measure of the resulting functional impairment.
This study assessed the performance of two unilateral lesion models of PD in a lateralised
nose-poking task in the nine-hole box test apparatus. This task assesses the accuracy
and speed of movements to either side of a rats' head, as well as a number of errors
of performance. Rats with complete unilateral dopamine depletion (induced by injection
of 6-OHDA into the medial forebrain bundle (MFB)) attempted fewer trials and committed
more procedural errors than controls. They developed a marked ipsilateral responding
bias, with a reduced accuracy for contralateral stimuli. They were also slower to
react to contralateral stimuli and to complete movements bilaterally. Rats with unilateral
nigrostriatal terminal lesions (induced by multiple injections of 6-OHDA in the striatum)
developed a similar pattern of deficits, but they were significantly less impaired
and spontaneously recovered to pre-operative levels by 4 months post-lesion. This
experiment confirms that the lateralised nose-poking task may be a powerful tool for
assessment of the nature of deficit and recovery in rats with complete but not partial
unilateral dopamine lesions.