2-Minute Neuroscience: L-DOPA

L-DOPA is an amino acid involved in the synthesis of the neurotransmitter dopamine, as well as the most common treatment for Parkinson’s disease. In this video, I discuss L-DOPA as a Parkinson’s disease treatment.

TRANSCRIPT:

L-DOPA is an amino acid involved in the synthesis of the neurotransmitter dopamine. When dopamine is produced in the brain, the amino acid tyrosine is first converted to L-DOPA and then L-DOPA is converted to dopamine. While dopamine administered as a drug cannot pass the blood-brain barrier to enter the brain, L-DOPA can, and this characteristic has helped to make L-DOPA the most common treatment for Parkinson’s disease.

Parkinson’s disease is characterized by the death of dopamine neurons in a region of the brainstem called the substantia nigra, and a subsequent deficiency of dopamine in a group of structures known as the basal ganglia. This dopamine deficiency is thought to contribute to the problems Parkinson’s patients experience with movement.

L-DOPA has a remarkable ability to reduce the symptoms of Parkinson’s disease in some patients. The generally accepted mechanism for this action is that the brain is able to use L-DOPA to synthesize more dopamine and replenish its depleted dopamine stores. While this does seem to be a main characteristic of L-DOPA’s mechanism, however, it is thought that L-DOPA may exert a therapeutic effect through other mechanisms as well, such as by acting as a neurotransmitter on its own. While L-DOPA can effectively treat the symptoms of Parkinson’s disease, it is not able to stop the neurodegeneration caused by the disease. Thus, Parkinson’s disease continues to progress even with L-DOPA treatment. Additionally, over time L-DOPA’s effectiveness begins to decrease and eventually movement problems, known as L-DOPA dyskinesias, may occur in response to L-DOPA treatment. L-DOPA dyskinesias typically involve quick involuntary movements, but may also include a number of other complications like uncontrolled muscle contractions or writhing movements. The mechanisms underlying L-DOPA dyskinesias are still not completely understood, and may involve factors like the continued death of dopamine neurons in the substantia nigra and fluctuations in dopamine levels caused by L-DOPA treatment.

REFERENCES:

Halbig TD, Koller WC. 2007. Levodopa. In: Koller WC, Melamed E, eds. Parkinson's disease and related disorders, Part II. Amsterdam: Elsevier.

Obeso JA, Stamelou M, Goetz CG, et al. Past, present, and future of Parkinson's disease: A special essay on the 200th Anniversary of the Shaking Palsy.
Mov Disord. 2017 Sep;32(9):1264-1310. doi: 10.1002/mds.27115.

Special thanks to Nicole Lookfong for help with fact-checking this video.