Amid reports that a drug used to treat Parkinson's disease has caused some patients to become addicted to gambling and sex, University of Pittsburgh researchers have published a study that sheds light on what may have gone wrong.
In the current issue of Proceedings of the National Academy of Sciences, Pitt professor of neuroscience, psychiatry, and psychology Anthony Grace and Pitt neuroscience research associate Daniel Lodge suggest a new mechanism for how the brain's reward system works.
The main actor in the reward system is a chemical called dopamine. When you smell, touch, hear, see, or taste a pleasurable stimulus, the dopamine neurons in your brain start firing in bursts. So-called "burst firing" is how the brain signals reward and modulates goal-directed behavior. But just how the stimulus you perceive causes neurons to switch into or out of this mode has been a mystery.
Using anesthetized rats, Lodge and Grace found that one area in the brain stem, known as the laterodorsal tegmental nucleus, is critical to normal dopamine function.
"We've found, for the first time, the brain area that acts as the gate, telling neurons either to go into this communication mode or to stop communicating," says Grace. "All the other parts of the brain that talk to the dopamine neurons can only do it when this area puts them into the communication mode."
As a result, disruption in that area may play a major role in dopamine-related brain function, both in normal behaviors and psychiatric disorders.
The brain area identified by the Pitt researchers is regulated by the "planning" part of the brain, the prefrontal cortex (PFC), thereby providing a powerful indirect means for the PFC to affect the activity of dopamine neurons. Such a link could explain how changes in the PFC, seen in disorders like schizophrenia and drug addiction, disrupt the signaling of dopamine neurons.
Source: University of Pittsburgh
Related stories:
Singing to females makes male birds' brains happy
The melodious singing of birds has been long appreciated by humans, and has often been thought to reflect a particularly positive emotional state of the singer. In a new study published in the online, open-access journal
PLoS ONE on October 1, researchers at the RIKEN Brain Science Institute in Japan have demonstrated that this can be true. When male birds sang to attract females, specific "reward" areas of their brain were strongly activated. Such strong brain activation resulted in a similar change in brain reward function to that which is caused by addictive drugs.
Do 'light' cigarettes deliver less nicotine to the brain than regular cigarettes?
For decades now, cigarette makers have marketed so-called light cigarettes — which contain less nicotine than regular smokes — with the implication that they are less harmful to smokers' health. A new UCLA study shows, however, that they deliver nearly as much nicotine to the brain.
Protein found that regulates gene critical to dopamine-releasing brain cells
Researchers have identified a protein they say appears to be a primary player in maintaining normal functioning of an important class of neurons – those brain cells that produce, excrete and then reabsorb dopamine neurotransmitters. These molecules command numerous body functions, ranging from management of behavior and mood to control of movement, and one day may hold the key to why and how some people develop Parkinson's and other brain diseases.
Surgical technique halts cell loss, Parkinson's researchers find
Deep brain stimulation, a surgical technique often viewed as a last resort for people with Parkinson's disease, halts the progression of dopamine-cell loss in animal models, according to preliminary research by scientists at the Neuroscience Institute at the University of Cincinnati (UC) and University Hospital.
The first autism disease genes
The autistic disorder was first described, more than sixty years ago, by Dr. Leo Kanner of the Johns Hopkins Hospital (USA), who created the new label 'early infantile autism'. At the same time an Austrian scientist, Dr. Hans Asperger, described a milder form of the disorder that became known as Asperger Syndrome, characterised by higher cognitive abilities and more normal language function. Today, both disorders are classified in the continuum of 'Pervasive Developmental Disorders' (PDD), more often referred to as Autism Spectrum Disorders (ASD).
UC team studies link between Parkinson's disease and depression
A patient who receives a diagnosis of Parkinson's disease might become depressed, and understandably so. But does the depression then exacerbate the progression of Parkinson's?
Cocaine: How addiction develops
Permanent drug seeking and relapse after renewed drug administration are typical behavioral patterns of addiction. Molecular changes at the connection points in the brain's reward center are directly responsible for this. This finding was published by a research team from the Institute of Mental Health (ZI) in Mannheim, the German Cancer Research Center (DKFZ) in Heidelberg and the University of Geneva, Switzerland, in the latest issue of
Neuron. The results provide researchers with new approaches in the medical treatment of drug addiction.
1 sleepless night increases dopamine in the human brain
Just one night without sleep can increase the amount of the chemical dopamine in the human brain, according to new imaging research in the August 20 issue of
The Journal of Neuroscience. Because drugs that increase dopamine, like amphetamines, promote wakefulness, the findings offer a potential mechanism explaining how the brain helps people stay awake despite the urge to sleep. However, the study also shows that the increase in dopamine cannot compensate for the cognitive deficits caused by sleep deprivation.