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The Callicam
Current Common Marmoset Research

Current Research - Page 7

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III. Biomedical Research (cont.)

C) Parkinson's Disease

  • Muscle tremors are the most noticeable characteristic of Parkinson's Disease
  • From the Parkinson's Disease model in marmosets a drug with treatment potential has been found

Parkinson's Disease (PD) is a disease that affects approximately 1.5 million Americans. PD occurs when the part of the brain that produces dopamine (a neurological chemical that transmits signals between certain brain cells) dies, therefore, causing a shortage of dopamine. Dopamine signaling between certain brain cells permits normal and smooth motor control and when there is a shortage the symptoms of PD begin to appear. PD is a chronic progressive nervous disease that appears later in life and is characterized by symptoms such as:

  • muscle tremors
  • muscle rigidity
  • a hunched posture
  • decrease in spontaneity and movement
  • problems with speech
  • problems with breathing

A person with PD will eventually loose control of all movements and become immobilized and possibly die.

In order to study the effects of possible successful treatments for PD, an animal model is required. Two strategies have been shown to produce PD in the common marmoset. The first involved producing bilateral 6-hydroxydopamine (6-OHDA)-lesions in a particular part of the brain called the "Nigra-Striatal Pathway." The 6-OHDA is a drug that is toxic only to brain cells that produce and release dopamine. Following the injection of 6-OHDA, common marmosets displayed behaviors characteristic of human PD patients, because dopamine signaling between brain cells has been destroyed. With such a PD model, drugs can be administered and monitored for potential treatments to counteract PD.

The 6-OHDA model is one that is used to study the long-term effects of drug treatments for PD. If an exploratory drug, however, is in need for preliminary testing the 1-methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated marmoset is utilized. MPTP produces similar PD symptoms to 6-OHDA because it also destroys dopamine producing cells. After administering MPTP to common marmosets they display PD symptoms such as muscle tremors and decreased movements. They, however, show a substantial behavioral recovery shortly after the administration of MPTP, thus allowing studies of short-term drug treatments.

One drug with potential for a treatment PD is L-dopa, a brain chemical from which dopamine is derived. It appears that L-dopa effectively reverses PD symptoms, although it does have unpleasant side-effects. L-dopa causes nausea, vomiting, and difficulty performing voluntary actions. Many researchers are, therefore, trying to combat these side-effects by administering L-dopa with other drugs. Unfortunately L-dopa does not retain its effects for reversing PD for long. Researchers, therefore, are trying to find a chemical equivalent of L-dopa using the MPTP-treated model because it is the most appropriate PD model available. By continuing research on the marmoset models researchers hope to decrease the millions of Americans suffering from PD.

Further Reading:

Hughes, N. R., Mitchelll, I. J., & Brotchie, J. M. (1996). The Bilateral 6-Hydroxydopamine-Lesioned Marmoset Model of Parkinson's Disease. The Basal Ganglia V, 505-510.

Pearce, R. K., Jackson, M., Britton, D. R., Shiosaki, K., Jenner, P., Marsden, C. D. (1998). Actions of the D1 Agonists A-77636 and A-86929 on Locomotion and Dyskinesia in MPTP-treated L-dopa-primed Common Marmosets. Psychopharmacology, 142, 51-60.

Additional related links:

Chicago Time Tribune archive articles:

  • (Oct. 30, 1999), "New Parkinson's Therapy Buoys Researches"

National Institute of Neurological Disorders and Stroke:

New York Times archive articles:

  • Health and Fitness (Feb. 2, 1999), "Twins Study Links PD to Environment"
  • National Desk (April 22, 1999), "Monkeys' Own Cells Reported to Reverse a Nerve Disorder"

Parkinson's Disease Foundation:

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Text by Rebecca Dallwig.