What Is the Nigrostriatal Pathway?

The nigrostriatal pathway is defined as the connection between two areas of the brain called the substantia nigra amd the striatum. The adjective nigrostriatal is a combination of the Latin words niger for the black color of the substantia nigra and stria for the striped constitution of the striatum. Their are four major dopamine, or dopaminergic, pathways of the brain, with the nigrostriatal pathway being one of them. This pathway is also considered part of the basal ganglia loop, which is a functional unit mainly associated with cognitive control.

Consisting of elongated neurons that are covered by myelin for electrical insulation usually referred to as white matter, the nigrostriatal pathway is generally classified as a neural pathway. Additionally, it is subcategorized as a dopamine pathway. This is because it is one of the connections that carry dopamine, a substance or neurotransmitter instrumental in facilitating movement. Thus, it is similar to other dopamine pathways such as the mesocortical pathway, mesolimbic pathway and tuberoinfundibular pathway.

The substantia nigra, which is Latin for "black substance," is the part of the brain that contains the dopamine. The nigrostriatal pathway transports the neurotransmitter from the substantial nigra, which is located in the mesencephalon, or midbrain, to the striatum in the lower part of the prosencephalon, or forebrain. Also known as the neostriatum or striate nucleus, the striatum is the primary input port of the basal ganglia, thus using the dopamine to assist in regulating movement.

Since dopamine is important in movement, some medical conditions have been linked to instances when there is a deficiency involving the nigrostriatal pathway. The occurrence of Parkinson's disease, a degenerative disorder that affects the central nervous system (CNS), is linked to the death neurons carrying dopamine that are located in the substantia nigra. As of 2011, the cause of the cells' death is yet to be determined. Also, the pathological signs do not become evident until the nigrostriatal pathway has lost at least 80 percent of its dopamine capability.

The nigrostriatal pathway is also clinically significant for inducing tardive dyskinesia. A type of disorder that involves an increase of involuntary movements, the medical condition is called "tardive" because the symptoms tend to develop slowly — long after onset of the disease. Tardive dyskinesia is linked to the side effects of anti-psychotic drugs, which are used to treat mental disorders, such as schizophrenia and manic depression. This is because such medications block dopamine receptors that pathways like the nigrostriatal pathway carry.