Profiling changes in gait dynamics resulting from progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced nigrostriatal lesioning.

ABSTRACT

Current behavioral measurements for motor impairment are not consistently sensitive in rodent models of partial nigrostriatal dopamine (DA) depletion. In addition to exploratory and somatosensory behavior, motor skills that are thought to be directly translatable to human Parkinson's disease patients are assessed. However, many of these motor tests require the training and learning of particular tasks, so it cannot be determined whether impairments are due to motor or to learning deficit. Therefore, we have quantified multiple temporal and spatial indices of gait dynamics in a model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced partial nigrostriatal lesioning using a treadmill apparatus requiring no prior training. Three days following the cessation of progressively increased MPTP administration, rearing and foot-fault behaviors showed significant deficit. Ten days after the final MPTP injection, gait dynamics were assessed and indicated differences between MPTP- and vehicle-treated animals. The major significant changes were in stride length, frequency, duration, and number of steps. Three weeks following a progressively increased dose of MPTP (administered 5 days per week over the course of 4 weeks), mice showed a 63% decrease in tyrosine hydroxylase-immunoreactive (TH-ir) nigrostriatal neurons in the substantia nigra pars compacta and a 72% decrease in TH-ir terminals in the caudate-putamen. This suggests that there is a continued effect of progressively increased MPTP on nigrostriatal DA neurons, correlated with rearing and foot-fault behaviors and further characterized by differences in temporal and spatial measurements of gait dynamics.