Phenylethylamine, also known as 2-phenylethylamine or phenethylamine, is a substance best known for its natural occurrence in the nervous system of humans and other mammals, where it is believed to act as a neurotransmitter or neuromodulator. It has stimulant effects and is important to the neurochemistry of infatuation and romantic love. It is a trace amine and a natural monoamine alkaloid. In the human brain, it causes the release of the neurotransmitters norepinephrine and dopamine. There are also large numbers of derivatives of phenylethylamine, many of which are used medically or recreationally.
Phenylethylamine is most prominent for the role it plays during feelings of infatuation, limerence, or romantic love, when it stimulates the release of greater amounts of dopamine and norepinephrine. Dopamine is strongly tied to sexual drive, feelings of pleasure, and the brain's reward system. Norepinephrine causes heightened attention and increased heart rate and is closely tied to the fight-or-flight response. Together, these neurochemicals result in many of the feelings associated with romantic love, including sexual desire, giddiness or euphoria, and nervousness.
There has been speculation that consuming foods that naturally contain large amounts of phenylethylamine, such as chocolate, might mimic these effects or have other psychological benefits. Similarly, pills with the neurotransmitter are often marketed due to the chemical's supposed weight-loss benefits or effects on mood. However, phenylethylamine consumed via the digestive system is metabolized too rapidly for significant amounts to reach the brain, so ingesting it in food, pills, or supplements is typically unlikely to have therapeutic effects. People who suffer from attention deficit-hyperactivity disorder or clinical depression often have lowered levels of phenylethylamine, while schizophrenia sufferers have elevated levels.
There is are many chemical compounds, collectively called phenethylamines, based on phenylethylamine's chemical structure with atoms added or substituted. These include the categories of substituted phenethylamine, substituted amphetamines, and substituted methylenedioxyphenethylamines. Many of the chemicals in these groups have significant effects on the human nervous system and are used as psychoactive drugs, including amphetamine, methamphetamine, and methylenedioxymethamphetamine, better known as MDMA or ecstasy. The use or possession of some phenethylamines is restricted or banned in many jurisdictions. Some phenethylamines also have medical uses and are used in decongestants, antidepressants, and in treatments for respiratory problems such as asthma.
