Oxytocin Flashcards
what is the structure of OT
small
9 aa peptides (nonapeptides) with 1 internal disulphide bridge (S-S)
how do AVP and OT differ
by 2 aa
what is a neurophysin
carrier protein for OT and AVP within vesicles
where is OT synthesised
magnocellular Neurons (SON and PVN)
OT release
packaged in neurosecretory vesicles and transported to axons
released from neurohypophysis, neural lobe, and pars nervosa (terminal that form posterior pituitary) and are released from blood
where do the parvocellular neurons project
they are small
no projection to the PP
only project to the CNS (amygdala, BS,hippocampus)
3 peripheral actions of OT
milk ejection reflex
uterine contraction during parturition
inhibit CRH in males
steps in the milk ejection reflex
myoepithelial cells express OT R
milk is inside the alveoli lumen
MC contract
milk is squeezed out of lactiferous duct
signalling for milk ejection reflex
sensory neurons in nipple
info travels from: SC to mesencephalon/diencephalon to hypothalamus
increased firing of OT in SON/PVN
synchronised burst discharged
what does synchronised burst discharge lead to
increased intramammary pressure (rapid contraction)
plasma OT levels spike
rapid contraction - mammary gland reflex
steps in uterine contraction during parturition
OT R on myometrial cells in uterus
Oestrogen stimulates OT R production on myometrial cells
uterine distention (stretching) releases OT
plasma OT levels increase during the final stages of labour
role of syntocin
synthetic OT
administered to deliver baby/placenta
(not essential as OT antagonists/KO still deliver)
OT endocrine action in males
no physiological role
released during ejaculation may enhance sperm transport?
inhibits CRH secretion (releases ACTH-releases cortical the stress hormone)
central role of OT (paracrine/autocrine)
OT stored and released from dendrites of magnocellular cells
upregulated by lactation
central roles of OT (neuromodulator actions)
stereotypical maternal behaviour
pair bonding (m&f)
social behaviour (trust/morality/empathy)
maternal behaviours which release OT
parturition
suckling
sexual activity
Kendrick (2002)
icv injection of OT ant reduces pup licking in rats
OT requires estrogen – induce maternal behaviour in virgin rats
(sheep) vaginal/cervical stimulation (VCS) induces maternal behaviour and bonding
AVP - no effect on maternal behaviour
what do plasma OT levels correlate to in humans
parental affection and bonding
maternal affection
paternal parenting behaviour
voles
praire voles - monogamous (pair bonding /biparental care) OT induces bonding without mating
meadow voles - polygamous & solitary
Gobrogge & Wang (2015)
praire voles spent increased time with partner
meadow voles spent increased time alone
CRISPR KO of OT R in praire voles
pair bonding still occurs and parental behaviours
OT R not essential for social attachment in praire voles
pair bonding in humans
OT release causes pair bonding
sex (orgasm/ejaculation)
plasma OT is a surrogate for central release
associated with the limbic system (VMN/amygdala)
what does intranasal OT cause
altered perception of social qualities
increased trust and generosity
increases perception of attractiveness and trustworthiness
disorders due to central OT dysfunction
ASD
OCD
PTSD
ASD
valproic acid induces ASD symptoms
reduced ultrasonic vocalisation, repetitive stereotypical behaviours
decrease in CSF OT
