Parkinson's Disease (PD) is a chronic and progressive movement disorder that results from the loss of substantia nigra and dopamine producing cells. The four primary symptoms of PD are tremor, or trembling in hands, arms, legs, jaw, and face; rigidity, or stiffness of the limbs and trunk; bradykinesia, or slowness of movement; and postural instability, or impaired balance and coordination. There are a number of animal models that attempt to mimic the symptoms of PD, including chemical induced models and transgenic models. Models with which PsychoGenics has experience include the Reserpine Induced Hypoactivity rat model and the 6 hydroxydopamine mouse model.