Dopamine: Its role in the brain
Like other neurotransmitters, dopamine helps in the transmission chemical messages between nerve cells through the synapse. This is a junction that occurs between the postsynaptic membrane and the presynaptic nerve cell. Membrane storage cells secrete dopamine at the synapse. This dopamine then passes through the synapse, binds with the postsynaptic receptor membrane and activates dopamine-receptors. The excess dopamine is repackaged and returned to the storage vesicles. It is not possible to determine the exact amount of dopamine lost, but all humans experience a gradual loss of this substance as they age. In Parkinson’s, dopamine is lost at a higher rate. Both imaging studies and biochemical measurements suggest that dopamine loss can occur long before motor symptoms. Pars compacta is an area of the substantia-nigra that shows a degeneration of neurons producing dopamine. The loss of dopamine causes a disruption in voluntary motor control, which results in Parkinson’s symptoms.
