The role of dopamine
Dopamine just like other neurotransmitters help in the transmission of chemical messages from one nerve cell the other through the synapse, a junction between the postsynaptic receptor and the pre-synaptic cell. Membrane storage vesicles secrete dopamine in the synapse and this dopamine passes through synapse and then binds to the postsynaptic membrane thus activating dopamine receptors. However, the excess amount of dopamine goes back to storage vesicles through repackaging. Although, it is impossible to measure the exact loss of dopamine cell but there is a progressive loss of dopamine with advancing age in all humans. While in the case of Parkinson’s disease, the loss of dopamine occurs at a much higher rate and both imaging studies and biochemical measures suggest that there is a potential loss of dopamine long before the appearance of motor symptoms. The degeneration of dopamine producing neurons is quite evident in pars compacta, which is a part of the substantia nigra. The significant loss of dopamine increases the disruption of voluntary motor control and results in the characteristic symptoms of Parkinson’s disease.