Two new test methods to quantify motor deficits in a marmoset model for Parkinson's disease

The validity of the common marmoset (Callithrix jacchus) as a model for human disease depends on the development of parameters with clinical relevance. We tested the effect of treatment with MPTP in two newly developed non-invasive motor behavioral paradigms in the context of Parkinson's disease. The "Tower" was designed to quantify the marmoset's natural jumping behavior as a measure for akinesia, the "Hourglass" to test the marmoset's natural righting reflex as measure for rigidity, analogous to axial motor behavior in humans. MPTP treatment affected marmoset behavior in both testing paradigms. The marmoset's righting reflex in the Hourglass remained significantly impaired during the full 3-week period after the MPTP intoxication. In the Tower, the marmosets were not able to jump the largest distances one week after MPTP and showed a persistent reduction in activity during the 3-week period after the MPTP intoxication. Because not all aspects of motor behavior are similarly affected by MPTP, a complete behavioral sketch of parkinsonian marmosets should preferably include a range of motor behavior functions to create an overview of the full range of motor impairments. Both the Hourglass and Tower test provide important behavioral parameters in a clinically relevant multiple testing approach in motor disorder models.