ABSTRACT
Parkinson’s disease (PD) is considered a slow progressive neurological disorder associated with defects in the function of the extrapyramidal system in the brain which controls voluntary movements. This disease is also associated with nonmotor decits and neurological symptoms, including impaired olfaction, autonomic failure, cognitive impairment, and psychiatric symptoms. PD is the commonest form of neurodegenerative diseases after Alzheimer’s disease. It is estimated that in normal individuals about 3-5% of dopaminergic (DA) neurons are lost every decade; however, in PD patients, the rate of loss is greater than that found in normal individuals.1 The analysis of autopsied samples of PD brain revealed that about 70-75 of DA neurons are lost at the time the disease becomes detectable. This suggests that DA neurons possess a high degree of functional plasticity.
