Addiction: Insights from Parkinson's disease

February 26, 2009

A new comprehensive review by researchers at the Montreal Neurological Institute (MNI), McGill University and the University of Cambridge, England provides vital insights into the neurological basis of addiction by investigating Parkinson's disease patients, who in some instances develop various addictions when undergoing medical treatment. The review, published in this week's (February 25) issue of the scientific journal Neuron, illustrates that persistently elevated levels of dopamine in the brain promote the development and maintenance of addictive behaviours.

Addiction is a complex health and societal problem that can destroy lives and damage communities. Brain imaging studies have shown that addiction severely alters brain areas critical to decision-making, learning and memory, and behavior control. In order to learn how to control or manage the disorder, it is necessary to understand the underlying biological mechanisms. Researchers have turned to Parkinson's disease to study addiction, successfully using one disease to learn about another. Although seemingly very different, dopamine plays a role in both disorders and some of the same systems in the brain are affected. Parksinson's disease is often thought as just affecting movement but, it also consists of cognitive, behavioural and mood symptoms, which are now being recognized as a major source of disability.

Dopamine is a neurotransmitter, or chemical messenger in the brain that is involved in brain processes that control movement, emotional response and the ability to experience pleasure, reward and pain. Parkinson's patients lack dopamine and are often treated with dopamine agonists, medication that mimics dopamine action.

"In some instances Parkinson's disease (PD) patients become addicted to their own medication, or develop behavioural addictions such as pathological gambling, compulsive shopping or hypersexuality," says Dr. Alain Dagher, neurologist at the MNI and co-author of the review.

"This is surprising because PD patients typically have a very low incidence of drug abuse and display a personality type that is the opposite of the typical addictive personality. These rare, addictive syndromes, which appear to result from excessive dopaminergic treatment, illustrate the link between dopamine, personality and addiction."

PD patients treated with dopamine agonists had an incidence of pathological gambling as high as 8% compared to less than 1% in the general population. In PD patients who develop addictive disorders, the problems started soon after starting dopaminergic therapy and stopped after treatment was discontinued. It was found that adjusting the dosage and combination of medication resolved the addictive symptoms, while maintaining the same motor benefit.

The phenomenon of addiction induced by dopamine medications can also tell us something about vulnerability to addiction in the general population. Not everyone is equally vulnerable, and it now appears that the propensity to become addicted is in part hereditary. Many of the genes implicated in addiction appear to affect brain levels of dopamine.

Studies show that that dopamine acts in an area of the brain known as the ventral striatum, which receives input from other areas such as the hippocampus and amygdala. It may be through this region that dopamine promotes addictive behaviours.

Understanding brain function that leads to drug addiction may help in the development of drugs to block drug-craving and drug-seeking behaviours in the general population as well as refine disease treatment for Parkinson's patients.

McGill University

---

---

	Meet Your Happy Chemicals: Dopamine, Endorphin, Oxytocin, Serotonin by Loretta Graziano Breuning PhD (Author) Humans have emotional ups and downs because we’ve inherited the operating system of earlier mammals. You feel good when you find new rewards because that triggers dopamine. You feel good when you get respect because it triggers serotonin. Building trust triggers oxytocin, and endorphin makes you feel good when you’re injured. The mammal brain releases happy chemicals when you do things that promote survival in the state of nature. You can get more happy chemicals from your brain when you understand the job it evolved to do. Happy chemicals were not meant to surge all the time. They evolved to reward you when you promote the survival of your genes. You define this in unique individuals ways because early experience builds the neural pathways that turn on the happy chemicals. But...
	Dopamine Handbook by Leslie Iversen (Author), Susan Iversen (Author), Stephen Dunnett (Author), Anders Bjorklund (Author) The discovery of dopamine in 1957-1958 was one of the seminal events in the development of modern neuroscience, and has been extremely important for the development of modern therapies of neurological and psychiatric disorders. Dopamine has a fundamental role in almost all aspects of behavior: from motor control to mood regulation, cognition and addiction and reward, and dopamine research has been unique within the neurosciences in the way it has bridged basic science and clinical practice. Over the decades research into the role of dopamine in health and disease has been in the forefront of modern neuroscience. The Dopamine Handbook is the first single-volume publication to capture current progress and excitement in this dynamic research field.
	The Craving Brain: A bold new approach to breaking free from *drug addiction *overeating *alcoholism *gambling by Ronald A. Ruden (Author) Where do the roots of addictive behavior lie -- in our genes or in our environment, in our chemistry or in our character? In the Craving Brain, Dr. Ronald Ruden asserts that the roots of addiction most defintetly do not lie in our character. Rather, they lie in a complex chain reaction that originates in an ancient survival mechanism in the brain. When this system is inappropriately activated, it drives the body to crave, sometimes with addictive behavior as the end result. In clear, straightforward language, Dr. Ruden outlines his remarkable successful treatment program which he believes can cure this problem.The Craving Brain offers crucial insights into the world of addiction. This revolutionary book will bring hope to millions of people who suffer from a wide range of addictions, from...
	The Dopamine Receptors (The Receptors) by Kim A. Neve (Editor) As sites of action for drugs used to treat schizophrenia and Parkinson’s disease, dopamine receptors are among the most validated drug targets for neuropsychiatric disorders. Dopamine receptors are also drug targets or potential targets for other disorders such as substance abuse, depression, Tourette’s syndrome, and attention deficit hyperactivity disorder. Updated from the successful first edition, "The Dopamine Receptors" serves as a reference work on dopamine receptors while also highlighting the areas of research that are most active today. To achieve this goal, authors have written chapters that set a broad area of research in its historical context, rather than focusing on the research output of their own laboratories.
	The Dopaminergic Mind in Human Evolution and History by Fred H. Previc (Author) What does it mean to be human? There are many theories of the evolution of human behavior which seek to explain how our brains evolved to support our unique abilities and personalities. Most of these have focused on the role of brain size or specific genetic adaptations of the brain. In contrast, Fred Previc presents a provocative theory that high levels of dopamine, the most widely studied neurotransmitter, account for all major aspects of modern human behavior. He further emphasizes the role of epigenetic rather than genetic factors in the rise of dopamine. Previc contrasts the great achievements of the dopaminergic mind with the harmful effects of rising dopamine levels in modern societies and concludes with a critical examination of whether the dopaminergic mind that has evolved in...
	You Never Miss the Dopamine...: (until the brain runs dry!) by Bill Schmalfeldt (Author) From the author of "No Doorway Wide Enough," "Undercover Trucker," and "Hunky Dunk," a real-life look at how one man deals with his Parkinson's disease decline by laughing at it. Told in a series of essays from his blog, Bill Schmalfeldt talks more about the non-motor symptoms of PD -- the speech difficulties, the bizarre dreams, the memory problems and the hallucinations -- in a way that makes the reader realize that while there's no cure for PD, it can't damage the human spirit (unless you let it)!
	Imaging Dopamine by Paul Cumming (Author) Since its discovery 50 years ago, brain dopamine has been implicated in the control of movement and cognition, and is concerned with diverse brain diseases such as Parkinson's disease, schizophrenia and drug addiction. This book is an illustrated biography of the dopamine molecule, from its synthesis in the brain to its signalling mechanisms and ultimately to its metabolic breakdown. Using colour illustrations of positron emission tomography (PET) scans, each chapter presents a specific stage in the biochemical pathway for dopamine. Writing for researchers and graduate students, Paul Cumming presents a compilation of all that has been learned about dopamine through molecular imaging, a technology which allows the measurement of formerly invisible processes in the living brain. He reviews...
	Molecular Origins of Human Attention: The Dopamine-Folate Connection by Richard C. Deth (Author) This volume provides a highly integrated view of attention-related events, taking the reader from individual molecular interactions through the regulation of neuronal circuits to our higher order capacity for selective amplification of particular information. Neuroscientists, psychologists, psychiatrists and other professionals dealing with psychiatric illnesses such as ADHD, autism, and schizophrenia will find this volume a useful addition to their library.
	Dumb Bells & Dopamine: A Parkinson's Success Story by Arthur Curren (Author) This book is about living with Parkinson's, an incurable, debilitating disease caused by the loss of dopamine-producing cells in the brain of the afflicted person. Levodopa is the only drug that replaces some of the dopamine and exercise is the only activity that induces the brain to produce dopamine. The author uses a rigorous exercise program to reduce the dosage of levodopa and extend the useful life of this essential drug. This is the author's dumb bells and dopamine approach to controlling Parkinson's.The author has also addressed some of the social issues related to the disease. This includes dealing with less than perfect physicians and with the negative situations that exist in the insurance industry and Social Security Administration.To provide real assistance to people with the...
	Overcoming qEEG Abnormalities and Reward Gene Deficits During Protracted Abstinence in Male Psychostimulant and Polydrug Abusers Utilizing Putative Dopamine ... Therapy: Part 2 (Postgraduate Medicine) by JTE Multimedia Background It is well established that in both food- and drug-addicted individuals there is “dopamine resistance” associated with the DRD2 gene A1 allele. Based on earlier studies, evidence is emerging wherein the potential of utilizing a natural, nonaddicting, safe, putative D2 agonist may play a significant role in the recovery of individuals with reward deficiency syndrome, including those addicted to psychoactive chemicals. Findings Positive outcomes demonstrated by quantitative electroencephalographic (qEEG) imaging in a randomized, triple-blind, placebo-controlled, crossover study involving oral Synaptose Complex KB220Z™ showed an increase of alpha waves and low beta wave activity in the parietal brain region. Using t statistics, significant differences observed between...