Dopamine

Dopamine is a chemical naturally produced in the body. In the brain, dopamine functions as a neurotransmitter, activating dopamine receptors. Dopamine is also a neurohormone released by the hypothalamus. Its main function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary.

Functions of Dopamine in the Brain

Role in Movement

Dopamine is critical to the way the brain controls our movements and is a crucial part of the basal ganglia motor loop. Shortage of dopamine, particularly the death of dopamine neurons in the nigrostriatal pathway, causes Parkinson's disease, in which a person loses the ability to execute smooth, controlled movements.

Related Topics:
Basal ganglia - Nigrostriatal pathway - Parkinson's disease

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Role in Cognition and Frontal Cortex Function

In the frontal lobes, dopamine controls the flow of information from other areas of the brain. Dopamine disorders in this region of the brain can cause a decline in neurocognitive functions, especially memory, attention and problem solving. This function is particularly related to the mesocortical dopamine pathway.

Related Topics:
Frontal lobes - Neurocognitive - Memory - Attention - Problem solving - Mesocortical dopamine pathway

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Role in Pleasure and Motivation

Dopamine is commonly associated with the 'pleasure system' of the brain, providing feelings of enjoyment and reinforcement to motivate us to do, or continue doing, certain activities. Certainly dopamine is released (particularly in areas such as the nucleus accumbens and striatum) by naturally rewarding experiences such as food, sex, use of certain drugs and neutral stimuli that become associated with them. This theory is often discussed in terms of drugs (such as cocaine and amphetamines) which seem to be directly or indirectly related to the increase of dopamine in these areas, and in relation to neurobiological theories of addiction, which argue that these dopamine pathways are pathologically altered in addicted persons. The mechanisms of cocaine and amphetamine are different, however. Cocaine acts as a dopamine transporter blocker, competively inhibiting dopamine uptake to increase the lifetime of dopamine. On the other hand, amphetamines act as dopamine transporter substrates to competitively inhibit dopamine uptake and increase the dopamine efflux via a dopamine transporter.

Related Topics:
Reinforcement - Nucleus accumbens - Striatum - Food - Sex - Associated - Cocaine - Amphetamines - Neurobiological

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

However, the idea that dopamine is the 'reward chemical' of the brain, a view held by many during early stages of its research, seems too simple as more evidence has been gathered. Dopamine is known to be released when unpleasant or aversive stimuli are encountered, suggesting that it is not only associated with 'rewards' or pleasure. Also, the firing of dopamine neurons occurs when a pleasurable activity is expected, regardless of whether it actually happens or not. This suggests that dopamine may be involved in desire rather than pleasure. Drugs that are known to reduce dopamine activity (e.g. antipsychotics) have been shown to reduce people's desire for pleasurable stimuli, despite the fact that they will rate them as just as pleasurable when they actually encounter or consume them. It seems that these drugs reduce the 'wanting' but not the 'liking', providing more evidence for the desire theory.

Related Topics:
Neuron - Desire - Pleasure - Antipsychotic

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Other theories suggest that the crucial role of dopamine may be in predicting pleasurable activity. Related theories argue that dopamine function may be involved in the salience ('noticeableness') of perceived objects and events, with potentially important stimuli (including rewarding things, but also things which may be dangerous or a threat) appearing more noticeable or more important. This theory argues that dopamine's role is to assist decision making by influencing the priority of such stimuli to the person concerned.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~