Experimental models and behavioural tests used in the study of Parkinson's disease

The present review brings the survey of the most frequently used behavioural tests in experimental models of Parkinson's disease (PD). Although there is no spontaneous occurrence of parkinsonism in animals, several experimental animal models of PD have been developed to achieve the same clinical features in animals. The techniques employing neurotoxins in lesioning the nigrostriatal dopaminergic (DA) system have a large selectivity and reproducibility. The most frequently used neurotoxins are 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA). MPTP-lesioned monkeys mimic best the symptomatology of PD in human patients while rats appear to be refractory to MPTP. For that reason, 6-OHDA is used to damage the substantia nigra in a rodent model. Behavioural tests of animals with nigrostriatal lesion represent valuable non-invasive methods for assessing the influence of damaged DA system on locomotor activity. The most frequently used experimental model of PD is the drug-evoked rotation in 6-OHDA unilaterally lesioned rats. This model produces well-defined and stable behavioural deficits. The rotation test is a useful parameter for evaluating imbalances of dopamine in both striata of the hemi-parkinsonian rat model. T-maze, treadmill running test or sensorimotor tests are used to evaluate spontaneous locomotor activity of lesioned animals. Skilled motor tasks measure the influence of dopamine-depleting lesions on complex motor acts. Transplantation of DA tissue into the striatum offers a new approach to the treatment of PD. Experimental models and behavioural tests are used to evaluate the extent of graft-induced recovery of MPTP- or 6-OHDA-lesioned animals. Different results obtained after the use of different tests reflect the level of graft integration into the host circuitry.