The effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on the cognitive and motor functions in rodents: A systematic review and meta-analysis

Memory and motor deficits are commonly identified in Parkinson's disease (PD). 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is transformed to MPP+ via monoamine oxidase B (MAOB), which causes oxidative stress and destroys dopaminergic (DA) neurons in substantia nigra pars compacta (SNc) and is widely used to create animal models of PD. However, to-date, a comprehensive analysis of the MPTP effects on various aspects of PD does not exist. Here, we provide a systematic review and meta-analysis on the MPTP effects on memory and motor functions by analyzing 51 studies on more than one thousand animals mainly including rats and mice. The results showed that in addition to motor functions such as coordination, balance and locomotor activity, MPTP significantly affects various mnemonic processes including spatial memory, working memory, recognition memory, and associative memory compared with the control group with some differences between systemic and intra-nigral injections on spatial memory, familiar object recognition, and anxiety-like behaviors. Nevertheless, our analysis failed to find systematic relationship between MPTP injection protocol parameters reported and the extent of the induced PD symptoms that can be a cause of concern for replicability of MPTP studies.