Substantia nigra dopaminergic neuron loss 2023-04-09T17:19:52Z Melanin reduced in substantia nigra Ppigmented neurons in the substantia nigra produce the neurotransmitter dopamine. The loss of these neurons leads to the classical motor symptoms of Parkinson disease. The pigment contained within these neurons, termed neuromelanin because of its similar appearance to cutaneous melanin, is so abundant in the substantia nigra of the human brain that this structure can be seen macroscopically as a darkened area (hence the origin of the name given to this brain region) Degeneration and loss of neurons in the substantia nigra of the brain. Abnormal substantia nigra morphology