T 1/2 of oxytocin is -

Ans. is 'b' i.e., 3-4 minutes o Oxytocin has a half life of 3-4 minutes and duration of action of approximately 20 minutes.Oxytocino Oxytocin is a nonapeptide.o It is secreted by posterior pituitary along with vasopressin (ADH).o Both oxytocin and ADH are synthesized within the nerve cell bodies in supraoptic and paraventricular nuclei of hypothalamus; are transported down the axon and stored in the nerve endings within the neurohypophysiso They are stored in separate neurones as complexes with their specific binding proteins (Neurophysin). Its major actions are :1. Uterus# It increases the force and frequency of uterine contraction. Estrogens sensitize the uterus to oxytocin, while progestins decrease the sensitivity.# The increased contractility is restricted to the fundus and body, lower segment is not contracted, may even be relaxed at term.# Excessive uterine contraction prior to labor may cause fetal distress, placental abruption or uterine rupture.2. Breast# Oxytocin contracts myoepithelium of mammary alveoli and forces milk into bigger sinusuids - Milk ejection or milk letdown reflex.3. CVS# Higher doses cause vasodilation - Brief fall in BP., reflex tachycardia and flushing. The umblicle vessels are constricted oxytocin may help their clossure at birth.4. Kidney# Oxytocin in high doses exerts ADH like action - water retention can occur.o Oxytocin is used in -i) Induction of labourii) Uterine inertiaiii) Post-partum hemorrhageiv) Breast engorgementv) Oxytocin challenge test.