Parkinson's disease involves the death of a specific population of neurons in the brain that supply the neurotransmitter dopamine (DA). A group of molecules termed neurotrophic factors have been identified to prevent the death of DA neurons and thereby continue the ability of these cells to provide DA to the brain. Neurotrophic factors that normally provide support for DA neurons during brain development hold the most potential for protecting DA neurons in the adult and aged brain. The molecule pleiotrophin (PTN) is intricately involved in normal DA neuron development and to date has not been studied for its ability to protect DA neurons in animal models of Parkinson's disease. We will study the ability of PTN gene transfer to protect DA neurons and to facilitate long term functional recovery in an aged pre-clinical model of Parkinson's disease. If successful, this approach may point the way to a novel therapeutic approach for Parkinson's patients that may provide long-term benefits without disabling side effects.