The substantia nigra (or "black substance") is a group of neurons that are part of the basal ganglia. They play an important role in initiating fluid movement. Without the substantia nigra, it is impossible to get up from a chair, lift your hand to swat a fly, or lift your coffee mug. From the substantia nigra depart axons that release the neurotransmitter dopamine to the striatum.
To understand the function of brain regions, it is often useful to look more closely at certain diseases. Parkinson's disease, for example, can teach us much about the function of the substantia nigra. From the age of 45, the neurons in the substantia nigra begin to die off slowly, with a loss of about 1% per year. For most people, this is not a problem. However, individuals who already did not have many substantia nigra neurons or in whom the die-off is too rapid develop Parkinson's disease. When the number of neurons becomes less than 20-30% of the normal amount, the first Parkinson's symptoms arise. This is due to a shortage of dopamine.
Typical symptoms of Parkinson's disease include stiffened limbs, tremors, balance problems and a flattened facial expression. Patients also often have difficulty voluntarily starting a movement. It is a progressive disease, so the severity of symptoms increases.
Treatment of Parkinson's disease is possible to a limited extent. Because dopamine cannot cross the blood-brain barrier, administering it makes no sense. However, the building block of dopamine, L-dopa, can pass through this barrier and is converted into dopamine in the brain. Therefore, L-dopa is administered in pill form to Parkinson's patients. However, this is not effective in every patient and the effect of L-dopa decreases as the disease progresses.
Auteur: Bart Aben (translated by Melanie Smekal)