Posterior pituitary — oxytocin release
Pituitary · Oxytocin Gq Ferguson reflex
Oxytocin is released in bursts by neural reflexes — cervical stretch in labour and nipple stimulation in lactation — and acts on Gq-coupled receptors on myometrium and breast myoepithelium.
Traced from the start
- Supraoptic and paraventricular magnocellular neurones
- Posterior pituitary — oxytocin release
Detail
- Receptor
- Myometrial oxytocin receptor density rises steeply near term under oestrogen, which is why the same dose does little in early pregnancy
- Clinical use
- Oxytocin infusion for induction and augmentation; oxytocin or carbetocin in the third stage to prevent postpartum haemorrhage
- Antagonist
- Atosiban, used as a tocolytic
When it goes wrong
Prolonged high-dose oxytocin infusion in hypotonic fluid
Water intoxication: hyponatraemia, headache and seizures, because oxytocin has weak V2 activity
Excessive infusion rate during induction
Uterine hyperstimulation with fetal heart rate decelerations; stop the infusion, reposition, and consider tocolysis
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