Introduction

Parkinson's disease is a relatively common disorder of the nervous system that afflicts patients later in life with tremor, slowness of movement, instability and rigidity. Treatment of these cardinal features of the disease is a success story of modern science and medicine, as a great deal of disability can be alleviated through the pharmacological correction of brain dopamine deficiency. Unfortunately these therapies only provide temporary relief from early symptoms and do not halt disease progression. For that reason, neuroprotective and cell replacement strategies are being explored (Borta & Hoglinger, 2007). A major advance in the understanding of Parkinson's disease (PD) came when dopamine deficiency was discovered in the corpus striatum and substantia nigra (SN) of...