Navigation Links
Why dopamine freezes parkinson patients and drives drug addicts
Date:8/8/2008

CHICAGO -- Parkinson's disease and drug addiction are polar opposite diseases, but both depend upon dopamine in the brain. Parkinson's patients don't have enough of it; drug addicts get too much of it. Although the importance of dopamine in these disorders has been well known, the way it works has been a mystery.

New research from Northwestern University's Feinberg School of Medicine has revealed that dopamine strengthens and weakens the two primary circuits in the brain that control our behavior. This provides new insight into why a flood of dopamine can lead to compulsive, addictive behavior and too little dopamaine can leave Parkinson's patients frozen and unable to move.

"The study shows how dopamine shapes the two main circuits of the brain that control how we choose to act and what happens in these disease states, " said D. James Surmeier, lead author and the Nathan Smith Davis Professor and chair of physiology at the Feinberg School. The paper is published in the August 8 issue of the journal Science.

These two main brain circuits help us decide whether to act out a desire or not. For example, do you get off the couch and drive to the store for an icy six-pack of beer on a hot summer night, or just lay on the couch?

One circuit is a "stop" circuit that prevents you from acting on a desire; the other is a "go" circuit that provokes you to action. These circuits are located in the striatum, the region of the brain that translates thoughts into actions.

In the study, researchers examined the strength of synapses connecting the cerebral cortex, the region of the brain involved in perceptions, feelings and thought, to the striatum, home of the stop and go circuits that select or prevent action.

Scientists electrically activated the cortical fibers to simulate movement commands and boosted the natural level of dopamine. What happened next surprised them. The cortical synapses connecting to the "go" circuit became stronger and more powerful. At the same time, dopamine weakened the cortical connections in the "stop" circuit.

"This could be what underlies addiction," Surmeier said. "Dopamine released by drugs leads to abnormal strengthening of the cortical synapses driving the striatal 'go' circuits, while weakening synapses at opposing 'stop' circuits. As a result, when events associated with drug taking where you took the drug, what you were feeling occur, there is an uncontrollable drive to go and seek drugs."

"All of our actions in a healthy brain are balanced by the urge to do something and the urge to stop," Surmeier said. "Our work suggests that it is not just the strengthening of the brain circuits helping select actions that is critical to dopamine's effects, it is the weakening of the connections that enable us to stop as well. "

In the second part of the experiment, scientists created an animal model of Parkinson's disease by killing dopamine neurons. Then they looked at what happened when they simulated cortical commands to move. The result: the connections in the "stop" circuit were strengthened, and the connections in the "go" circuit were weakened.

"The study illuminates why Parkinson's patients have trouble performing everyday tasks like reaching across a table to pick up a glass of water when they are thirsty," Surmeier said.

Surmeier explained the phenomenon using the analogy of a car. "Our study suggests that the inability to move in Parkinson's disease is not a passive process like a car running out of gas," he said. "Rather, the car doesn't' move because your foot is jammed down on the brake. Dopamine normally helps you adjust the pressure on the brake and gas pedals. It helps you learn that when you see a red light at an intersection, you brake and when the green light comes on, you take your foot off the brake and depress the gas pedal to go. Parkinson's disease patients, who have lost the neurons that release dopamine, have their foot perpetually stuck on the brake."

Understanding the basis for these changes in brain circuitry moves scientists closer to new therapeutic strategies for controlling these brain disorders and other involving dopamine like schizophrenia, Tourette's syndrome and dystonia.


'/>"/>

Contact: Marla Paul
marla-Paul@northwestern.edu
312-503-8928
Northwestern University
Source:Eurekalert

Related medicine news :

1. Food restriction increases dopamine receptor levels in obese rats
2. Antidepressants Can Increase Depression, Impulsivity and Suicide Risk by Decreasing Dopamine
3. Identification of dopamine mother cells could lead to future Parkinsons treatments
4. Fear that freezes the blood in your veins
5. Study suggests loss of 2 types of neurons -- not just 1 -- triggers Parkinsons symptoms
6. Gene Mutation Linked to Parkinsons Disease
7. Parkinsons Linked to Risk of Alzheimers
8. XShares Supports Parkinsons Disease Foundation 50th Anniversary Educational Symposium
9. Parkinsons Institute research shows that nicotine reduces levodopa-induced dyskinesias
10. NSAIDs Protect Against Parkinsons Disease
11. Ceregene Completes Enrollment of Phase 2 Clinical Trial for Parkinsons Disease
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:5/24/2016)... ... May 24, 2016 , ... Loma Linda University Health (LLUH) ... hospital and expanded Children’s Hospital. Over 3,000 people looked on as the shovels hit ... the event photo slidehsow. , During the program, Richard H. Hart, MD, DrPH, ...
(Date:5/24/2016)... Los Angeles, CA (PRWEB) , ... May 24, ... ... devoted to everything egg freezing, today announced the official relaunch of its community ... to use their frozen eggs. Eggsurance's mission is to create a safe and ...
(Date:5/24/2016)... Orion, Michigan (PRWEB) , ... May 24, 2016 , ... ... Yoga. , The Yoga practice enhanced with Young Living Essential Oils, taught by ... - 8pm at the Lake Orion location. Yoga Flow is 6:30pm - 7:15pm followed ...
(Date:5/24/2016)... ... , ... In light of recent heavy flooding in Houston, Texas, Pelican Water ... throughout the Houston area. , Heavy floodwaters have led to destroyed waterways and flooded ... may not even be aware of the contamination of their water supply and thus, ...
(Date:5/24/2016)... California (PRWEB) , ... May 24, 2016 , ... "ProText ... times," said Christina Austin - CEO of Pixel Film Studios. , ProText Layouts Vol. ... within Final Cut Pro X . With ProText Layouts, video editors can create ...
Breaking Medicine News(10 mins):
(Date:5/23/2016)... May 23, 2016 According ... Share, Development, Growth and Demand Forecast to 2022 ... Other), by Application (Drug Discovery and Development, Proteomics, ... (Pharmaceuticals, Life Science and Biotechnology, Academic and Research ... Research, the global mass spectrometry market ...
(Date:5/23/2016)... , May 23, 2016 ... for detection of multiple diseases; ,Technology to be presented ... Yissum Research Development Company of the Hebrew ... into a research agreement with Aurum Ventures MKI, the technology ... development of a new diagnostic approach for early detection ...
(Date:5/23/2016)... -- The global  reprocessed medical devices market ... according to a new study by Grand View Research, ... the lack of centralized support for waste disposal in ... for reprocessed medical devices market. Additionally, the long-term cost-efficiency ... the original device is the high impact rendering driver ...
Breaking Medicine Technology: