Oxytocin
- Stimulates uterine contractions during childbirth, and also stimulates
milk ejection from the lactating breast in response to suckling.
- Nonapeptide
Release
- Control of release is via neurogenic feedback control mechanisms.
- Produced in hypothalamus and released in posterior pituitary
- positive feedback loop from corpus luteum in mammals
- Stimulation of nipple, reproductive tract causes oxytocin release.
- release stimulated by stimulation of vagina and nipples (also haemorrhage,
restraint, fear, mild apprehension)
- can be stimulated by oestrogen release
- release inhibited by loud noise, increased temperature, severe pain
Site of Action
- acts on uterus and mammary glands
- Oxytocin causes contraction of myoepithelial cells in mammary gland
alveoli (Milk ejection reflex)
- causes milk ejection by contraction of myoepithelial cells in mammary
gland
- stimulates rhythmic contractions of uterus to aid in expulsion of fetus
- also causes potentiation of CRH induced ACTH release and possibly
acts as prolactin releasing factor
Disorders
- deficiency causes inadequate milk ejection
14.2.2.2 oxytocin
| role in parturition, milk-ejection |
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