The hidden side of Parkinson's disease: Studying pain, anxiety and depression in animal models.

Parkinson's disease is a neurodegenerative disease leading to the loss of midbrain dopamine neurons. It is well known and characterized by motor symptoms that are secondary to the loss of dopamine innervation, but it is also accompanied by a range of various non-motor symptoms, including pain and psychiatric disorders such as anxiety and depression. These non-motor symptoms usually appear at early stages of the disease, sometimes even before the first motor symptoms, and have a dramatic impact on the quality of life of the patients. We review here the present state-of-the-art concerning pain, anxiety and depression-like parameters in animal models of Parkinson's disease.