Sex, Drugs, and the Brain. A chemical journey through pain and pleasure. Evolution of the Limbic System. Africanus had a brain about 1/3 the size of our modern brain. Africanus was primarily instinctive in behavior. Africanus was not capable of language.
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Sex, Drugs, and the Brain
A chemical journey through pain and pleasure
Africanus had a brain about 1/3 the size of our modern brain
Africanus was primarily instinctive in behavior
Africanus was not capable of language
Africanus had practically no prefrontal cortex and was probably not capable of weighing options
Yet, deep inside our brain is the brain of Africanus. Our limbic system has not changed greatly in 2 million years.
terminal button of neuron 1
dendrite of neuron 2
Simultaneous formation and destruction affords careful regulation of neurotransmitter levels in brain
The mesolimbic pathway aka the “pleasure center”
The mesolimbic pathway is your reward system for behavior that needs to be reinforced (eating, seeking warmth or shelter, sex, winning a fight, etc.)
Dr. Robert Heath
Dr. James Olds
Stimulation of the septum produces intense pleasure
mescaline (from Peyote cactus)
dopamine (from brain)
cathanone (from Kat)
phenylethylamine (from chocolate)
ephedrine (from Ephedra)
methamphetamine (speed, crystal meth, crank)
methylenedioxomethamphetamine (MDMA, XTC, love drug, E)
from a Peruvian tree
from Psilocybe Mexicana (Magic Mushroom)
from Ergot fungus
from Magic Mushroom
lysergic acid diethylamide(LSD, acid)
Dr. Albert Hoffman
Dr. Alexander Shulgin
Dr. Timothy Leary
Prof. Richard Alpert
Two year study of the effects of psilocybin analogs on the scholarly creativity of students
Used with permission from Wyeth-Ayerst Laboratories, 2005
This cockroach has an electrode array implanted in its brain, and can be steered by radio control
From Northwestern University, Chicago, IL
Think about sex
Think about love
Dr. Helen Fisher Rutgers University
Dr. Sue Carter University of Illinois
Dr. Karen Bales University of California
These researchers study the role of neuropeptides in pair-bonding (romantic love)
Prairie vole is a monogamous species. That is, it finds a mate and stays together for life
Its close cousin, the Montane vole, is non-monogamous. It never mates with the same partner twice
Yet, the Prairie vole and Montane vole have essentially the same brain. So, what causes this dramatic behavioral difference?
different by only two amino acid residues
Injecting oxytocin into a Montane vole will cause it to temporarily act like a Prairie vole
Injecting a Prairie vole with an oxytocin blocker will cause it to temporarily act like a Montane vole
In humans, oxytocin levels increase when we are in love, increase when we simply touch our pets, and, in women, increase dramatically just after childbirth
Hypothesis: Could oxytocin be the molecule of love?
high endorphin levels
High serotonin levels
Low endorphin levels
Sudden drop in serotonin
High endorphin levels
High serotonin levels
Low endorphin levels
Sudden drop in serotonin
A play in three acts
Meet the Players
aka Mr. Excitement
aka Mr. Desire
vasopressinaka Mother Superior
aka Mr. Happy
Scene 1: Testosterone elevates in the blood, signals the body to physically respond, and influences the decision making areas of the brain to “go for it”
Scene 2: Sensory information enters the brainstem triggering the release of dopamine in the ventral tegmentum
Scene 3: The ventral tegmentum fires a series of signals into the limbic system via the mesolimbic dopamine pathway
Scene 4: Norepinephrine elevates in the limbic system signaling the onset of pleasure. The hypothalamus and pituitary convert norepinephrine into adrenaline triggering a “fight or flight” response, resulting in emotional excitement
Scene 5: dopamine signals enter the septum, the main focal point of the “pleasure center”
Scene 6: dopamine signals reach the nucleus accumbens, reinforcing this behavior
Scene 7: dopamine signals make it to the prefrontal cortex, the decision making headquarters
Scene 8: the prefrontal cortex now makes a series of decisions, weighing options and consequences, and simultaneously stimulates the septum, nucleus accumbens, and amygdala
Enter stage left: Oxytocin and Vasopressin
As our lovers become increasingly enchanted with each others charms, the hypothalamus perks up and manufactures two neuropeptides, oxytocin (aka cuddles) and vasopressin (aka mother superior), and releases both of them into the cerebrospinal fluid. There they have full access to all the organs of the limbic system
Scene 9: Oxytocin binds to hippocampus, allowing the lovers to remember each other
Scene 10: Vasopressin binds to septum, dulling reward, and binds to amygdala causing warning signals, fear, and inhibition of attachment
Scene 11: Oxytocin binds to nucleus accumbens, causing memory of “pleasure” to associate with this particular person
Scene 12: The prefrontal cortex takes all sensory inputs, inputs from hippocampus, and inputs from memory, and goes into high gear to make decisions. These decisions are conveyed back to the limbic system as signals to the cingulate (“happy” vs. “unhappy”), amygdala (fear or threat of impending loss), septum (pleasure), and nucleus accumbens (habituation).
Scene 13: In the meantime, “cuddles” and “mother superior” are battling it out. If cuddles wins, you’re in love. If mother superior wins, you’re just having fun.
Scene 14: Oxytocin (cuddles) wins – you’re in love!
and all this happens in just 4 minutes
The scene takes place in the limbic system of a young man sitting with his date at the Underground Pub at York University on a Saturday night. There is no shortage of young women dancing a few feet away.
Testosterone: Look at that one. No, look at that one. No, look at that one.
Dopamine: Boy o boy o boy, is this gonna be fun or what?
Vasopressin: Don’t look at other girls, you’ll die
Testosterone: What’s a matter with you, yella? Reach over and hold her hand
Vasopressin: Don’t touch her hand, you’ll die
Oxytocin: Oh let’s hold hands all night and stare in her eyes, and hug
Testosterone: Hug, shmug! What a waste of time. Go for the gusto soldier!
Vasopressin: Stop! Do that and you’ll die
Testosterone: Oh, don’t listen to that you’ll do nothing. Go for the gusto soldier!
Oxytocin: I need a hug
Dopamine: Boy o boy, is this gonna be fun or what?
Vasopressin: If you listen to Sarge, you’ll die
All seems good with our lovers, BUT …..
Something nasty is happening in our lovers’ brains!!
All this limbic activity is dropping serotonin level fast and hard
Exit Stage Right
Within days, serotonin drops to levels mimicking that found in patients with obsessive-compulsive disorder
When our lovers are separated they literally obsess over each other.
Oxytocin acts as a serotonin reuptake inhibitor (naturally occurring Prozac). In about 6 months, serotonin is back to normal
Enter stage left - Serotonin
DISCLAIMER: As serotonin levels build, physical attraction between our lovers wanes. High oxytocin levels also inhibit the action of vasopressin and testosterone, further diminishing excitement in the relationship. This begins at about 17 months. There is about a 50% chance the relationship will end in roughly 4 years.
York University Department of Chemistry
Dr. Gillian Wu, Dean of Science and Engineering
Science Speakers Bureau
Dr. Susan Block
The Bonobo is a hominid and is our closest genetic relative sharing 99.7% of our genes
DEET (alarm pheromone for ticks, fleas, mosquitoes)
Hamsters (sex attractant)
Cockroach (sex attractant)
Gypsy moth (male sex attractant)
Truffles are mushrooms that grow underground
Female pigs can smell truffles over 1 meter underground. Sometimes they dig so ferociously that they have to be physically restrained.
HINT: They don’t eat them
1981 - Drs. Claus and Hoppen at the Technical University of Munich and Dr. Kong at the Lubeck School of Medicine independently found the active attractant in truffles
Sows exposed to pure androstenol become uncontrollably “sex-crazed”
Could androstenol be a human sex pheromone?
Let female humans smell androstenol and see if they become uncontrollably sex-crazed
Dr. Michael Kirk-Smith, University of Birmingham (every male graduate student volunteered to conduct the experiment)
CONCLUSION: androstenol makes women more attractive to women
So, is androstenol a real human sex pheromone?
Apparently not – social factors can override any pheromone control (if there is any)
But it’s sure being marketed like it is
The same company markets to you too
Muskone (from Musk Deer)
Exaltolide (synthetic analogue)
Martha McClintock, age 19
Harvard University psychology major
Dr. Mark Russel, Brain Behavior Research Institute, Sonoma State Hospital, California
Took the breast pads (unwashed) of over 100 nursing women and extracted them with alcohol
Treated handkerchiefs with the alcohol solution and had other women wear the handkerchiefs close to their faces for several days
The other women had a dramatic increase in sexual fantasies.
Breast “essence” from non-breastfeeding women had no effect.
No effect of any kind on men
Professor Martha McClintock
University of Chicago