The Role of Dopamine

Dopamine is one of the most important biological substances produced by the body. Though it is present in and functions analogously in many primates, dopamine is largely responsible for the experiences we think of as being human. A lack of dopamine also results in some of the darker and more unpleasant aspects of existence. Created in the brain, dopamine is at the center of how we experience the world and act the way we do.

Identification

• Dopamine is a neurotransmitter. It is a molecule that is released from the end of one neuron that attaches to the end of another, thus sending a chemical message. Dopamine, in fact, is the message. Special receptors on the ends of neurons are specially suited for dopamine and similar chemicals. When a molecule binds to these receptors, whether dopamine or an agonist that resembles dopamine, certain reactions occur. From these, as well as the symptoms that occur in dopamine deficiency, we can deduce the role of dopamine.

Movement

• Dopamine plays a role in smooth, controlled body movements. In the brain, the pathways of dopamine form important links between various parts, allowing the organ to function more smoothly as a whole. Cognition depends on access of information from other areas of the brain to the frontal cortex, which occurs along paths of dopamine transmission. Low levels of dopamine have been associated with Parkinson's disease, which is characterized by uncontrolled and shaky body movements.

Motivation and Pleasure

• Dopamine is most widely known, however, for being the neurotransmitter associated with pleasure. Any stimulus that produces any kind of positive response also stimulates the release of dopamine in the brain. The release of the dopamine links the stimulus to the positive feelings, creating anticipation of pleasure the next time the stimulus is introduced, and establishing a sort of biofeedback reward system. People and animals are motivated toward food, sex, drugs and other pleasurable stimuli because of the dopamine released in the brain.

Drugs

• The pleasurable effect of some drugs is due to the effect they have on dopamine reuptake. Normally, when dopamine is released, it gradually binds with neurons and is reabsorbed. Cocaine and amphetamines, in particular, block this reuptake and create an overabundance of dopamine between neurons, resulting in intensely pleasurable experiences. Other drugs, like opioids and cannabinoids, bind to unique neuron receptors. These drugs temporarily take the place of dopamine and modulate the feelings that would normally be controlled by dopamine.

Other Physical Reactions

• In addition to movement in general, dopamine is linked to some basic involuntary actions. Vomiting and feelings of nausea are inhibited by the presence of dopamine. Dopamine, which accounts for the pleasurable feelings of sex, is inhibited by prolactin, which is secreted after ejaculation in men. The resulting dip in dopamine is believed to explain the refractory period during which a man is unable to be aroused.

Dopamine Deficiencies

• Low levels of dopamine are indicated with a wide variety of diseases and disorders. Experience of pain is generally higher when dopamine is low, which is believed to explain the pain associated with Parkinson's disease. Difficulty socializing is also linked with low dopamine across a broad spectrum from simple anxiety to depression, schizophrenia and bipolar disorder.