Love and attraction

What is important for the formation and maintenance of relationships?

• Attraction

• Romantic love

• Attachment

• Love

• Pleasure

• Sex

• Addiction

Chemistry of attraction - pheromones

Substance produced by an organism that elicits a specific unlearned response in another member of the same species

Overlapping pheromones

Elephant and butterfly

Methyl paraben

Female dogs in heat secrete methyl paraben

Common preservative

Androstenone

Present in human sweat

Male sweat smell relaxes women

Truffles and boars produce androstenone, used in boar spray

Andron

First perfume to use androstenone

Androstenone is found in many perfumes

Highly effective?

Axe contains androstenone

Skatole

Produced by oral bacteria

• Flavor and fragrance industry makes large amounts

• Skatole is called civetole in perfumes

• Civet oil from the civet cat - $600 per kilo

  • Civetole for glamour

• Skatole naturally present in flowers

• Skatole is also an artificial flavor

Musk is a very expensive substance $100,000 per Kg

Synthetic musk is now used

Axe also contains musk ketone

Do human pheromones exist?

Human attraction is primarily visual

Romantic love stimulates chemical reward system

Phenethylamine

Released during romantic love increases dopamine levels

• Effects similar to cocaine, tobacco and amphetamines

• “feel-good” drugs

• Also found in chocolate

Dopamine vs serotonin in love

Increased dopamine during early stages of love causes serotonin to decrease

Serotonin controls mood

High levels = anxiety

Normal levels = balanced personality

Low levels = obsessive compulsive behaviour

Oxytocin

Long term attachment and bonding

• Oxytocin released during labor

• Oxytocin released during lactation

• Oxytocin and vasopressin released during intimacy

• Oxytocin antagonist leads to promiscuity

Voles and oxytocin

• Prairie voles produce oxytocin and are monogamous

• Mountain voles do not produce lots of oxytocin

• Injecting oxytocin does not produce monogamy in mountain voles

• Mountain voles lack the receptors

• Mountain voles did not have enough receptors

• Association between messenger and receptor depends on quantities of BOTH

Molecules and concentration

Molecules disassociate at low concentration

Molecules associate at high concentration

Aphrodisiacs

From the doctrine of signatures

• Rhino horn

• Common stinkhorn is just a mushroom

• Oysters

• Horny goat weed

• The Spanish fly is a beetle

  • Crushed beetles used in bull breeding

• Cantharidin is a dangerous irritant

• Internet versions contain capsaicin

  • Augustus Caesar

• Alcohol is the #1

Testosterone

Increases sex drive in men and women

Drugs and sex drive

• Cocaine may promote hypersexuality

• Ecstasy reduces inhibitions

• Alcohol is the number 1 aphrodisiac

• Too much alcohol impairs performance

Addyi

For Hypoactive Sexual Desire in Women

• Lack of sexual fantasies

• Low sex drive

Addyi has a long history

• Failed antidepressant (1997) 

  • Side effect noted in clinical trials was increased sexual desire in women 

• Clinical trials for Hypoactive Sexual Desire 

  • Failed FDA approval in 2010 

  • No benefits vs placebo 

• New clinical trials in 2013 

  • Placebo gave 2.5 satisfying sexual events/month 

  • Drug gave 3 satisfying sexual events/month 

• FDA approval in 2015 

  • Unmet therapeutic need

Benefits vs risks of Addyi

• Benefits 

  • Average of 0.5 extra satisfying sexual events per month 

  • 6 events per year

• Risk

  • Dizziness

    • 10 %

    • 3 % in placebo group

  • Somnolence

    • 10 %

    • 3 % in placebo group

  • Syncope

  • Low blood pressure

  • Patients must refrain from consuming alcohol

  • $9, 600/year (US)

Viagra

Was a failed blood pressure drug

• Safe 

• Rapidly entered the body 

• Inhibited a known enzyme phosphodiesterase 5 (PDE5) 

• PDE5 breaks down cGMP that promotes smooth muscle relaxation 

• Enhances blood flow