Social bonding Flashcards
Olfaction pathways in social bonding
Non-volatile olfactory cues e.g. pheromones processed by VNO which projects to AOB.
Bind to V1R & V2R (GPCRs) which initiate intracellular signalling cascade which opens TRP2 cation channels in membrane = depolarisation.
Projections to amygdala to activate reward pathways & elicit social bonds.
K/O studies (e.g. Keverne 2002, Haga 2010, Ferrero 2013) show this system is crucial for ID & social bonds.
Keverne 2002
K/O TRP2 = males try to mount other males instead of being aggressive towards them, females no longer aggressive to male intruders.
Haga 2010
Female rats can detect pheromone ESP1 in male tear fluid which primes her to be sexually receptive (show lordosis).
Ferrero 2013
Adult male rats can detect pheromone in juvenile females so don’t try to mate with them.
K/O TRP2 = try to mate with juvenile rats.
Prairie vole
Highly affiliative, biparental, male aggression to other males, monogamous.
Prefer partner in PPT.
Female prairie & OT
Vagino-cervical reflex arc during mating releases OT which feeds back to brain & activates OT circuits.
Inject OT without mating = bond, prefer partner in PPT.
OT antagonist = no bond.
No effect of OT in male prairies, or montane!
Male prairie & AVP
Inject AVP without mating = bond. AVP antagonist blocks this.
Increases affiliative and paternal behaviour.
No effect in female prairies, or montanes!
Young 1999
Differential distribution of V1ARs in male prairie: high in LS, VP (mesolimbic dopaminergic reward areas)
Young 2006
MRI shows differential distribution of OXTRs in female prairie: high conc in BST & NAc (mesolimbic dopaminergic reward areas)
Density correlates with strength of pair bond
Selective injection of OXTR antagonist (Young & Wang 2004)
Inject into NAc or PFC of female prairies = blocks partner preference.
No effect if injected to CP.
So only works in certain sites due to differential receptir distribution.
D2R/OXTR antagonists in female prairies (Young & Wang 2004)
D2 (but not D1) antagonist injected into NAc abolished partner preference in female prairies.
Injection of D2 agonist restored this, but could be blocked by OXTR antagonist.
Shows both DA & OXT receptor signalling is crucial for pair bond formation in female prairies.
Donaldson & Young 1998
AAV transfer of expanded microsatellite region of V1AR prairie gene into montane vole = increased expression of AVPRs in reward areas of brain so montane forms pair bonds & becomes monogamous.
Young 1999
Transgenic mice with expanded prairie vole gene = monogamous.
Landgraf 2003
K/O V1AR gene = impaired social recognition. Continue investigating known rats etc.
Rescued by AAV injection of receptor to LS = can now recognise individuals long-term.
Bartels & Zeki 2004
fMRI: images of love activate areas of human brain implicated in OT & AVP signalling.
van Ijzendoorn 2012
OT increases in-group trust & ability to judge emotional expression, so has positive impact on human social / affiliative behaviour.
Israel 2008
Long allele polymorphisms of human V1AR gene = more altruistic behaviour
Walum 2008
RS3 gene implicated. Long allele versions = more perceived marital problems.
Walum 2012
Genetic variation of OXTR gene in women associated with pair bonding strength
Pritchard 2007
Association between polymorphisms on V1AR gene & age of first sexual encounter in both sexes.
Also variation in OXTR gene in women linked to tendency to be a young mother.
Domes 2010
Intranasal OT increased FFA activation in face emotion processing task = better social recognition behaviour.
Choleris 2003
OT K/O mice impairs recognition, so will investigate novel mouse repeatedly. But main olfactory system unaffected!
K/O OE = also no social memory.
Shows both are crucial for normal social recognition: OE produced by ovary modulates OT signalling pathways to amygdala.
Rilling & Young (2014) - MPOA
MPOA monitors course of pregnancy via circulating sex steroids.
Robustly activated by pup stimuli.
So responsible for aversive to approach transition by enhancing mesolimbic dopaminergic pathway.
VTA also responds to pup stimuli by increasing DA concs in NAc.
D1 agonists in NAc produces maternal care without hormone injections.
Stolzenburg & Numan 2011
Injecting OE, OT or DA into MPOA of virgin rats elicits maternal responsiveness to pups.
i.e. aversive to approach.
Rilling & Young 2014 - oxytocin
OT injections induce maternal behaviour in mammals e.g. rats, sheep.
Even in virgins (e.g. rat blood transfusion).
Hormonal priming mechanisms at end of pregnancy
Surge of OE (& low P) = high OE:P ratio at end of pregnancy feeds back to brain so upregulates expression of OTRs in PVN of hypothalamus and in amygdala.
= primes brain circuits for maximum sensitivity to OT.
VC reflex arc during birth (& also suckling) releases OT which also feeds back to create surge of OT release from PVN.
VCS can induce OT release & therefore maternal behaviour, yet this is blocked by OT antagonist.
Produces immediate maternal response but also hard-wired circuits so prolonged maternal bond.
Reward pathways in mother-infant bonding
Lesion amygdala = ewes show maternal behaviour but not selective. Also reduces maternal behaviour in rhesus monkeys (Toscano 2009).
Lesion MPOA = no mother-infant bond even with hormonal injections (Rilling & Young 2014).
MPOA has inputs from PVN & amgydala.
Output to VTA (major dopaminergic output pathway).
Dopaminergic neurons from VTA form inhibitory synapses on NAc (GABAergic) which inhibits VP output.
Increased input to MPOA = increase output from dopaminergic VTA cells = increase output of VP limbic-motor reward system (Rilling & Young 2014).
Donaldson 2008
Long RS3 allele (linked to autism) = increased fMRI amygdala activation during face viewing task.
Gingrich 2000
Mating in female prairie voles leads to 51% increase in extracellular DA in NAc. Inject haloperidol (DAR antagonist) = blocks mating-induced pair bonding. So dopaminergic pathways crucial for pair bonding.
Aragona 2003
D2 is crucial for initial pair bond formation, while upregulation of D1 in males post-mating may prevent formation of new pair bonds.
Liu 2003
Injection of OXT antagonist into NAc blocks partner preference induced by activation of D2Rs, while injection of D2R antagonist blocks pair bonds formed by activation of OXTRs.
Suggests OXT and DA signalling occur concurrently and it is their interaction in the NAc that results in pair bond formation to specific individual.
Babb 2010
RS3 gene not present in truly monogamous spider monkeys.
