Nigrostriatal pathway
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The nigrostriatal pathway is a neural pathway which connects the substantia nigra with the striatum. It is one of the major dopamine pathways in the brain, and is particularly involved in the production of movement, as part of a system called the basal ganglia motor loop.
Loss of dopamine neurons in the substantia nigra is one of the main pathological features of Parkinson's disease, leading to a marked reduction in dopamine function in this pathway. The symptoms of the disease typically do not show themselves until 80-90% of dopamine function has been lost.
This pathway is also implicated in producing tardive dyskinesia, one of the side effects of antipsychotic drugs. This medication (particularly the older typical antipsychotics) blocks D2 dopamine receptors in multiple pathways in the brain.
The desired clinical effect of reducing psychotic symptoms is thought to be associated with blocking dopamine function in the mesolimbic pathway only. However, as many of these drugs are not selective, they block dopamine in all pathways. When this happens in the nigrostriatal pathway, similar movement problems to those found in Parkinson's disease can occur.
Other major dopamine pathways include: