Tuesday, 11 December 2012

Dopamine, a brief description

Dopamine is a simple organic chemical in the catecholamine family, or a monoamine neurotransmitter which has a number of important physiological roles in the bodies of animals.
In the brain, dopamine functions as a neurotransmitter a chemical released by nerve cells to send signals to other nerve cells. Dopamine is produced in several areas of the brain, including the substantia nigra and the ventral tegmental area.It is a neurohormone that is released by the hypothalamus. Its action is as a hormone that is an inhibitor or prolactin release from the anterior lobe of the pituitary.

Dopamine was first synthesized in 1910 by George Barger and James Ewens at Wellcome Laboratories in London, England. In 1958, Arvid Carlsson and Nils-Åke Hillarp, at the Laboratory for Chemical Pharmacology of the National Heart Institute of Sweden, discovered the function of dopamine as a neurotransmitter. Arvid Carlsson was awarded the 2000 Nobel Prize in Physiology or Medicine for showing that dopamine is not just a precursor of norepinephrine and epinephrine but a neurotransmitter, as well.
Dopamine plays a major role in the brain system that is responsible for reward-driven learning. Every type of reward that has been studied increases the level of dopamine transmission in the brain, and a variety of highly addictive drugs, including stimulants such as cocaine and methamphetamine, act directly on the dopamine system. There is evidence that people with extraverted (reward-seeking) personality types tend to show higher levels of dopamine activity than people with introverted personalities.
Several important diseases of the nervous system are associated with dysfunctions of the dopamine system. Parkinson's disease, an age-related degenerative condition causing tremor and motor impairment, is caused by loss of dopamine-secreting neurons in the substantia nigra. Schizophrenia has been shown to involve elevated levels of dopamine activity in the mesolimbic pathway and decreased levels of dopamine in the prefrontal cortex. Attention deficit hyperactivity disorder (ADHD) and restless legs syndrome (RLS) are also believed to be associated with decreased dopamine activity.
Dopamine is also used as medication. It acts on the sympathetic nervous system. Application of dopamine leads to increased heart rate and blood pressure. When administered through an IV line, dopamine does not cross the blood brain. It acts on the heart by raising its contractility and blood pressure, this is useful in heart failure.
Dopamine cannot cross the blood-brain barrier, so dopamine given as a drug does not directly affect the central nervous system.
Dopamine is needed in some brain diseases as well. This includes diseases such as Parkinson's disease and dopa-responsive dystonia. For these patients levodopa is used. This is a precursor of dopamine. It can cross the blood-brain barrier.
Exercise to increase dopamine levels in the brain naturally. According to specialists regular, vigorous exercise can be just as effective for treating mood issues as medication and therapy. 30 minutes of daily exercise, including aerobic exercise, for overall brain health. Weight training is especially helpful for increasing dopamine. Replace caffeinated soda, coffees and teas drink decaffeinated green tea Restricting your food intake increases dopamine receptors.
Eat lean proteins, beans and vegetables to increase dopamine production in the brain. According to experts, eating lean beef, pork, turkey and chicken facilitate dopamine production. Eating cold water fish, wild game, bison and ostrich helps to produce dopamine. Other foods that increase dopamine are low-fat dairy products, fava beans, edamame, black beans, chick peas, lima beans, lentils, nuts and seeds. Leafy vegetables and green, yellow and red vegetables provide nutrients which indirectly facilitate dopamine production.
While Foods such as sugar, saturated fats, cholesterol, and refined foods interfere with proper brain function and can cause low dopamine.
When dopamine levels are depleted by stress, certain antidepressants, drug use, poor nutrition, and poor sleep. Alcohol, caffeine, and sugar all seem to decrease dopamine activity in the brain.
Low dopamine levels can cause depression, loss of motor control, loss of satisfaction, addictions, cravings, compulsions, low sex drive, poor attention and focus. When dopamine levels are elevated symptoms may manifest in the form of anxiety, paranoia, or hyperactivity.
When a person is depressed, symptoms like a lack of motivation and a reduction in the pleasure he or she experiences in life may be persistent. These symptoms are thought to be caused by lower levels of dopamine. Many doctors prescribe medications that increase dopamine in the brain to help those suffering from major depression. Increasing dopamine is also thought to help with depressive moods in those who have bipolar disorder.
Levels of dopamine in the brain, especially the prefrontal cortex, help in improved working memory. However, this is a delicate balance and as levels increase or decrease to abnormal levels, memory suffers. Dopamine helps in focus and attention. Vision helps a dopamine response in the brain and this in turn helps one to focus and direct their attention. Dopamine may be responsible for determining what stays in the short term memory based on an imagined response to certain information. Reduced dopamine concentrations in the prefrontal cortex are thought to contribute to attention deficit disorder.
Scientists found, had fewer dopamine receptors than normal-weight subjects. Compared with the obese group, the number of dopamine receptors decreased as the subjects' body mass index, an indicator of obesity, increased. That is, the more obese the individual, the lower the number of receptors. It's possible that obese people have fewer dopamine receptors because their brains are trying to compensate for having chronically high dopamine levels, which are triggered by chronic overeating. However, it's also possible that these people have low numbers of dopamine receptors to begin with, making them more vulnerable to addictive behaviors including compulsive food intake.
The researchers note that, based on this study alone, they cannot conclude whether the brain changes they've detected are a consequence or a cause of obesity. They also acknowledge that the regulation of body weight is extremely complex, involving many physiological mechanisms and neurotransmitters. But they do suggest that addressing the dopamine receptor deficiency or finding other ways to regulate dopamine in obese people might help reduce their tendency to overeat.

Unfortunately, many of the drugs that have been shown to alter dopamine levels are highly addictive. But exercise, which has other obvious benefits in weight control, is another way obese subjects might be able to stimulate their dopamine pleasure and satisfaction circuits, the researchers suggest. In animal studies conducted elsewhere, exercise has been found to increase dopamine release and to raise the number of dopamine receptors. This suggests that obese people might be able to boost their dopamine response through exercise instead of eating  just one more reason to exercise if you're trying to lose weight.
The neurobiology of aggression is not well understood, but scientists are aware of a relationship between the neurotransmitter serotonin and certain aggressive behaviors. The objective of this study was to explore whether higher levels of another brain chemical called dopamine, involved in pleasure and reward, increased aggressive response in its subjects. To scientists' surprise, it was not as they first theorized.
"The results of this study were astonishingly opposite of what was previously hypothesized," says Ingo Vernaleken, M.D., lead author of the study and research scientist for the department of psychiatry at RWTH Aachen University in Aachen, Germany.
"Subjects with more functional dopaminergic reward-systems were not more aggressive in competitive situations and could concentrate even more on the game. Subjects with lower dopaminergic capacity were more likely to be distracted by the cheating behavior."
In this study, 18 healthy adults in their twenties were tested for aggression using the psychological behavioral task known as the point subtraction aggression paradigm (PSAP). Participants were asked to play a computer game that required them to press a bar multiple times with the incentive of winning money, but they were also told that an adversary in the next room who is able to cheat may steal some of their winnings. What the paranoid participants did not know was that there was no adversary. The computer program is designed to perform randomized deductions of the subjects' monetary reward to simulate the cheating competitor.The participant had three choices to react: punish the cheater, shield against the adversary by repeatedly pressing a defense button, or continue playing the game in order to maximize their ability to win cash, which indicated resilience.
Results of the study showed a significant impact on aggressive response in areas in the brain where dopamine synthesis was present, especially in the basal ganglia, which among other functions include the motivation center. Minimized aggression was associated with higher dopamine levels in both the midbrain and the striatum, which plays a role in planning and executive function. People with greater capacity for dopamine synthesis were more invested in the monetary reward aspect of the PSAP, instead of acting in defense or with aggression against their perceived adversary, whereas subjects with lower capacities had a higher vulnerability to act either aggressive, defensive or both. A well-functioning reward system causes more resilience against provocation, excluding the behaviors of a competitive personality that is mistaken for aggressive behaviour. The fine balance of dopamine can alter anything from motivation or movement to attention and perhaps aggression. While increase dopamine reduces Impulsivity the slight connection to behaviour might be related to the Dark Triad of personality traits. The dopamine reward system has a complex web of mechanisms not just for motivation but also behavior, which relates to our animal programming. Perhaps in the end when we look to progress in science or extend our families we can thank the rewards triggers of our animal brains... or at least monitor the manifestations for low Dopamine levels.  

No comments:

Post a Comment