Lecture 15 - Oxytocin Flashcards
Attachment is critical for humans
Parental attachment
Partner attachment
Trust
Key for our development and happiness
Evolved to allow for survival and propagation of species
Co-opted for more nuanced attachments
Oxytocin basics
Oxytocin is a hormone
Neuropeptide in PVN and SON (Supra orbital nucleus)
Direct projection to posterior pituitary
Oxytocin released increases through pregnancy
Fetal DHEAS from adrenals
Thinning cervix and contractions
PVN and SON fire in unison: cause pulses of oxytocin to start labour and then positive feedback loops that go in
Stimulates prolactin release
oxyticin projects to VTA Nac and PFC important for motivated behaviour and perceptions of what is rewarding, projections to the amygdala suggest modifications of emotional responses and Hippocampus suggests role in memory
Projections of oxytocin center
Post pit Olfactory bulb Medial Preoptic Area Amygdala Hippocampus Limbic System
Oxytocin initiates labour
+ve feedback via prostaglandins
Oxytocin is increased in all placental mammals at labour
Enhanced by increased receptors
(a) Estrogen increases oxytocin receptors on the uterus
(b) Oxytocin is released from mothers and fetus pituitary
(c) this 1 - stimulated the uterus to contract and 2 - stimulates the placenta to make prostaglandins
Prostaglandins both reinforce uterus contraction and feedback positively to make more oxytocin
So it is a positive feedback loop
Ramps up to the point of birth
Synthetic oxytocin: Pitocin/Synotocin
Labour induction in 25% women
After labour, what to OT do?
Development of Maternal Behavior
Virgin/non-maternal rats cannibalize babies
Intracerebral oxytocin + E2
Maternal behaviour in virgin female rats
MPOA or VTA
Antagonism OT blocks maternal behaviour
True in sheep too
Farmers induce fostering
OT wont cros the BBB so you need to put it in the spine to have these effects
Auditory cues and maternal behavior
Ultrasonic call of pup
Activate auditory cortex
OT receptors
Makes them more responsive
OT release at birth stimulates these receptors
More responsive to pup cry
Make virgins react to pup cry with OT to the auditory cortex
Makes pups more likley to live
OT stimulates auditory and olfactory processing of pup cues
Drives start of maternal behaviour
Oxytocin initiates lactation
Oxytocin at labour: initial push for lactation
Physical stimulation of nipples:
Oxytocin contracts mammary glands
Prolactin instigates milk production
(one is not enough)
Suckling also increases milk production while the infant feeds
Lactation and maternal behaviour
Pups nuzzle mother’s ventral surface back arches and crouch over her pups.
Kyphosis
And checking pups are ok
Licking and grooming
Contact with ventral surface stimulates more OT
Important for maternal behavior and activation of MPOA, VTA and NAc
These are all important for reward learning which makes it more likely the mother will keep being a good mom
Learning of maternal behavior and bond
Human Maternal Behaviour
Oxytocin is important for human labour
Used for induction
Oxytocin also stimulates mammary glands for nursing
Repeated behavior for (feeding from milk letdown)learning
Important for maternal bond?
Does oxytocin also affect maternal behavior in humans?
Evidence for neuro basis of human affiliation
Examined oxytocin during pregnancy and 1 month postpartum
OT from blood samples
Interview with mother on parenting experience
Maternal preoccuopation, attachment representation, checking on infant etc
Videotaped a 15min interaction between mother and child
Blind coders using Feldman scale of attachment
Results
Variation in oxytocin and cort across pregnancy, found elevated levels in 1st trimester but highest in 3rd
Is this variation related to maternal behavior?
Negative correlation between oxytocin and cort
Positive correlation between oxytocin and maternal behavior -Related to maternal preoccupation -Related to attachment representation -NOT related to checking behavior (this is more anxiety)
Oxytocin is related to development of maternal behaviour
Oxytocin and Paternal Care
What about Dad’s?
Oxytocin important for paternal bond?
Mothers and fathers interacting with their children
Scored as low or high affection by observing physical touching
Measured oxytocin in saliva following contact with children
Does oxytocin increase following in males interacting with offspring?
Oxytocin is not different at baseline for moms or dads BUT
Increase in oxytocin only in high affection parents
Role for oxytocin in maternal and paternal bond
Gaze in Sexual Desire vs Romantic Love
Men and women looked at photographs to rapidly determine if they elicit:
romantic love in them
sexual desire in them
Tracked their eye movements to determine where they were looking to make their decision
No sex differences in eye movement
Fixate more often on face when see images determined to be romantic love
Face and eye contact important in romantic love
Oxytocin increases gaze to eyes
Can administer oxytocin via intranasal spray
Leaps and bounds in research
If oxytocin and gaze are both important for bonding maybe oxytocin affects gaze
Intranasal oxytocin effects on gaze to human faces (photos)
Pictures shown for 2sec each
Decreases gaze to forehead and cheeks
Increases gaze to eye and mouth region in OT spray condition
Oxytocin playing an important role in bonding in general
Oxytocin and development of maternal behaviour
Lamb fingering
Administer oxytocin to cause ewe to foster lamb
Vaginocervical causes ewe to foster lamb too
Genital stimulation = oxytocin
Nipple stimulation =oxytocin
back in the day before had synthetic oxytocin nfarmers could cause this with manual vaginocervical stimulation. Turns out this causes oxytocin release too, so see stim of primary and secondary sex organs cause oxytocin release. Get release of this hormone important in mother child bond.
Has implications for how sex will affect bonding – release of oxytocin in the presence of a sexual partner will drive the formation of a bond, particularly in women for whom oxytocin is more abundant than males. T^hat is what we are really looking at today – the role of oxytocin in romantic relationships. Goint to do that using a lot of research from a new type of rodent, the vole!!
Oxytocin in developing a Pair Bond
Stimulation of breasts and vagina during sex can cause release of oxytocin
Oxytocin release during sex might initiate romantic bond
Monogamy in animals
Socially monogamous
Will still bang around
Bonding in Voles
So how is a Prairie vole different from a Montane vole?
Hormonal differences responsible for differing behavior
Oxytocin?
SO prarie voles form monogamous family units, at least some of the time, while mountain voles do not. Lets take a bit more time to go through the reason these sub-species are thought to be distinct
Lower maternal care in single parent units lead to the cvole equivalent of low licking and grooming in rats. See longterm effects on parenting behaviour, but also on future pair bonding….suggests a similar mechanism for maternal and partner bonds
Oxytocin released during sex
Male and female
Oxytocin manipulation on sex and bonding more effective in Prarie Voles
Difference in oxytocin receptor distribution
Higher in the NAc, PFC, and hypothalamus
Same amount of oxytocin has greater effect
So there is the same amount of OT release (and endorphin, but not topic today. However OT has much larger effect on mating and parental behaviour in prarie – if same OT levels HOW???
Receptor distribution – touched on this last class, but central today – distributin of receptors key. Same amount of hormone but way more recptors for binding means that hormone can have a greater effect. Exactly what Young and others figured out. Although OT levels the same, the difference in receptors, with waaaay more in Prarie voles, suggested that this hormone has greater effect
There is much more OT receptors in the prarie vole than the montane one and in their nucleus accumbens (involved in reinforcement learning) so social learning is being reinforced
Increasing OT receptors in voles
Working Hypothesis:
Prairie voles are more parental and form pair bond because they have more oxytocin receptors
Does increasing oxytocin receptors (OXTR) in Prairie voles increase parenting behavior and pair bonding?
Adeno-associated viral vector: overexpress OXTR
Examine parental behavior and partner preference 2 months later
SET UP
Juvenile female Prairie voles
Adeno-associated viral vector (AAV) gene transfer
Over express OXTR during puberty
DNA viruses use cells DNA and RNA machinery to reproduce themselves
Insert gene into virus and virus into Prairie vole nucleus accumbens
Increase production of gene of interest (OXTR)
Test alloparental behavior and partner preference ~2 months later
Longterm effects of elevated OXT receptors
RESULTS
Note that these were nulliparous voles, meaning they had not had a litter of pups themselves. When they were testing response to pups they used pups from another mother. Thus Prarie voles would be expected to show some care, but relatively low since not their own offspring and had not gone through the pregnancy and birth process that we now know helps to foster a bond and care behavior via hormones.
GFP is a visal tag put onto the virus so you can see what brain areas it actually affected. This is essentially a control group – got the same tag for visualization but no change in DNA sequence to produce oxytocin receptors
Soo have a group with no brain injection (Sham), we have one with this injection but no virus to alter OTR, we have a group where he was aiming for the Nac but hit a different region, and finally, we have the group with elevated OTR because of this virus.
Increase lick and groom pups only with increased OXTR in Nac, so increased parental behaviour, good start but looked at other behaviours too.
Partner Preference Test
Female and male together for either 6 hours
NOT normally long enough to form pair
Separated for 30min before preference test
Time spent immobile with both voles
Typically need at least 12 hours together for a strong bond to form, so in theory these females should not be bonded yet. Wanted to test if the increase in OTR could increase
Increased time spent with partner after only with increased OXTR in NAc
Oxytocin in the NAc
Critical for formation of bonds
Parental and partner
Individual differences in prairie voles based on OXTR in NAc
Done with Montagne voles too = behave more like prarie voles
Do humans behave like voles?
In voles: parental behaviour from increased action of oxytocin and vasopressin
Visual, tactile, olfactory cues from pups stimulate hormone release
Pair bonds between adults based on higher activation of oxytocin and vasopressin systems
In humans: both men and women, oxytocin levels rise dramatically during offspring care giving and romantic interactions
Visual, tactile and olfactory stimulation can have these effects
The human brain manufactures and uses vasopressin and oxytocin in much the same way
Maternal behavior in an expectant mother arises from hormonal changes that her system induces, and after birth it usually stems from hormones her offspring stimulates. Breast feeding causes some of the stimulation.
Vasopressin enters the bloodstream during sexual arousal, and oxytocin at orgasm (Carmichael, et al. 1994; Insel, Carter 1995). In both female and male humans, oxytocin levels rise dramatically during sex, and may promote the associated feelings of love and infatuation. A simple touch can release oxytocin. Humans share many of the oxytocin and vasopressin responses of animals.
Oxytocin in human pair bonds
Difficult to study –when will a human pair bond will start??
Research on associated emotions/behaviours
Intranasal oxytocin administration:
Decreases hormonal and psychological stress response
Increases eye gaze and trust (game theory)
Increases ability to read others emotions
Suggest oxytocin might facilitate healthy relationships
STUDY
Intranasal oxytocin
administered to both members of a couple
Discuss a “conflict issue” for 10min
Measure stress hormones and interaction during conflict
Oxytocin increase positive:negative interactions
Oxytocin resulted in decrease in stress hormone cortisol
Greater effect on women’s cortisol
Sex differences in oxytocin function: role in sexual orientation
Oxytocin plays greater role in female pair bonding than in males
Organized early in life like other sex difference in hormones (e.g. LH)
Differences in hetero and homo -sexual male response to oxytocin?
Reduced early life androgens hypothesized to contribute to homosexual orientation
“Feminized” response to oxytocin?
STUDY
Intranasal administration of oxytocin to hetero and homo –sexual men
Happy, neutral and angry faces rated
Oxytocin in women increases perception of faces as trustworthy
Suggests that oxytocin has greater effect in homosexual men than hetero, similar to the difference seen btween men and women
Oxytocin in human pair bonds
Summary
Associated with behaviours that support healthy relationships
Increased empathy, trust, and eye contact
Reduced stress
Increasing oxytocin increases positive:negative interactions in couples
Role in committed human relationships
Greater role in females
Gonadal hormone organization and activation contribute to sex differences in oxytocin
Oxytocin effects differ between hetero and homo -sexual males
Support of biological basis for homosexuality
Oxytocin increases bonding and trust…..
Oxytocin promotes social attachment and affiliation in animals
Also affect prosocial approach behaviors - such as trust?
Major marketing push for perfume/cologne
However, we may be overstepping in some of these assessments….
