Chemical

Lessons for Lovers

Romantic love is mental illness.  But it's a pleasurable one.  It's a drug.
It distorts reality, and that's the point of it.  It would be impossible to fall in love with someone that you really saw.
- Fran Lebowitz
 

Love is an irresistible desire to be irresistibly desired.

- Robert Frost
 

One type of love originates in the hypothalamus (a part of the brain also present in other animals).  It is programmed into DNA. A chemistry between lovers is not just a turn of phrase; it is a torrential release of brain chemicals and hormones.

Chemistry Chart

Testosterone - This hormone, produced in both men and women, regulates sexual desire and too much is counterproductive.
Progesterone - A testosterone antagonist, it lowers sex drive (in the pill as well).  It is a mild sedative and has a calming effect.
Estrogen - Makes women sexually attractive and more receptive.  


Phenylethylamine - A neurotransmitter released by a region of the brain called the hypothalamus, produce in capillaries and in catecholaminergic terminals.  Phenylethylamine, or PEA, causes you to fall madly in love with someone.  It is a natural form of amphetamine that floods the regions of the brain involved in sexual excitement.  It generates feelings of euphoria.  But it doesn't work alone when you are attracted to someone.  People who profess high passion for each other have equally high levels.  So-called "love at first sight" causes a circulatory surge.  The decay rate means the effects last only 18 months to five years in a given relationship - long enough to procreate and protect a child during early years of life.  Affairs and second (or third) marriages can cause the clock to be reset.
Dopamine - Involved in the "attention-getting" phase of attraction, it signals the brain that a reward is possible and helps to focus the attention.  Under the influence of dopamine, people are more talkative and excitable.  It is released when a person smokes a cigarette (one of tobacco's addictive components) and is a factor in attention deficit disorder.  It promotes action.
Serotonin - Helps to control mood and reduce its fluctuations.  A shortage of this brain chemical is widely associated with depression, so antidepressant drugs such as Prozac are designed to increase serotonin levels (as can pleasant conversation with your friends).  High levels make you feel good about yourself and encourage mate selectivity but it may sometimes increase violent behaviour and thrill-seeking when levels are too high.  Lower amounts are associated with less discriminating choices of mates and overly aggressive sexual behaviour.
Norepinephrine - Adrenalin: this neurotransmitter gets your blood racing and primes you for action.  As part of the "fight or flight" response, it floods the brain while you are deciding whether to kill or kiss.
Prolactin - Decreases sex drive, especially in men.
Endorphins - Produced in the brain; released in response to touch and sex, they produce overall positive feelings.
Oxytocin - Secreted from the pituitary gland, it bathes the brain and reproductive tracts of both women and men.  This chemical wash increases sensitivity to touch and encourages grooming and cuddling in both sexes.  It reduces stress-causing hormones in the body and influences bonding between adults (friends as well). It keeps relationships together after phenylethylamine has decayed.  "Touch deprivation" depletes the supply and sends people running to their hairdresser or masseuse.  Consuming several alcoholic drinks can decrease it. Stimulating oxytocin levels generates affection.  Oxytocin and its role in affection is one reason for such youthfulness.
Vasopressin - Hormone produced by the pituitary, it is an antidiuretic (causes water retention), increases blood volume and also blood pressure.  It is identified as the "monogamy molecule" and modulates testosterone.  It levels extremes of feelings (including anger), and increases focus in lovemaking.
Chocolate - The fats in dark chocolate trigger the brain's production of natural opiates.  Three compounds in chocolate enhance a feeling of well-being: anandamide, a cannabinoid which activates the same receptors in the brain as the active ingredient in marijuana and two compounds which increase the appetite.
Pheromones - Chemicals in the body that send signals to others through a subliminal passageway of scent called the vomeronasal system.
DHEA (dehydroepiandrosterone) - Secreted by adrenal glands, it is a weak androgen.  Most sex hormones and and pheromones are derived from it.  Males and females have roughly equal amounts in their bloodstream.
Cultural belief in passionate love forever is misplaced!

Source: http://www.flatrock.org.nz/topics/drugs/you_dont_need_love.htm