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In page Putamen:

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Dopamine is a neurotransmitter that has a dominant role in the putamen, most of it is supplied from the substantia nigra. When a cell body of a neuron (in the putamen or caudate nuclei) fires an action potential, dopamine is released from the presynaptic terminal. Since projections from the putamen and caudate nuclei modulate the dendrites of the substantia nigra, the dopamine influences the substantia nigra, which affects motor planning. This same mechanism is involved in drug addiction[citation needed]. In order to control the amount of dopamine in the synaptic cleft, and the amount of dopamine binding to post synaptic terminals, presynaptic dopaminergic neurons function to reuptake the excess dopamine.