Oxytocin milk ejection

OT receptors are localized ia the brain hypothalamus, limbic system, cortex, striatum, olfactory system, and brain stem. In the periphery, OT is best known for its stimulation of uterine smooth muscle and the milk ejection reflex. Thr , Om ]oxytocin(l—8),... 

Posterior pituitary Two hormones, vasopressin and oxytocin, are synthesised in the hypothalamus and then transported through nerve axons to the posterior pituitary, where they are stored until released. Vasopressin acts on the kidney to conserve water. Its secretion is stimulated by thirst and a decrease in blood pressure. Secretion of oxytocin initiates uterine contraction for parturition. It also stimulates milk ejection from the mammary glands. 

Oxytocin (Pitocin, Syntocinon) causes milk release (letdown) by stimulating contraction of the myoepithelial cells of the milk ducts in lactating mammary glands this forces milk from the alveoli of the breast. Oxytocin release is stimulated by suckling and by auditory and visual stimuli, such as a baby s cry. Oxytocin is available as a nasal spray, which is used as an aid to lactation when milk ejection is impaired. 

Oxytocin may be given by intravenous infusion (e.g., labor induction), intramuscular injection (e.g., control of postpartum bleeding), or as a nasal spray (e.g., to promote milk ejection). 

Oxytocin, a nine amino acid peptide, is synthesized primarily in the paraventricular and supraoptic (SON) nuclei of the hypothalamus, from which it is released to the general circulation through the posterior pituitary (Insel et ah, 1997). However, oxytocinergic fibers have also been found to project from the PVN to the limbic system and several autonomic centers in the brain stem. This central OT pool appears to be independent of pituitary OT release cerebrospinal fluid (CSF) and plasma OT responses to numerous stimuli are not correlated (Insel, 1997). Oxytocin and its analog (or partner) peptide vasopressin are found only in mammals. A related peptide, vasotocin, thought to be the evolutionary precedent of these peptides, is found in reptiles and birds. The first known actions of OT were its peripheral effects on the physiology of new mothers. In mammals, OT stimulates milk ejection and uterine contraction, essential aspects of maternal physiology (Insel et ah, 1997). 

Oxytocin (OT) is a nonapeptide in which six amino acids form a ring closed by a disulfide bridge, while the ring itself forms an antiparallel pleated sheet. The tail portion of the peptide, composed of Pro-Leu-Gly-NHj, is also rigidly held in a folded conformation. Oxytocin causes the powerful contraction of some smooth muscles and plays a vital role in milk ejection (not to be confused with milk secretion, which is regulated by prolactin). It also has uterotonic action, contracting the muscles of the uterus, and is therefore used clinically to induce childbirth. 

Oxytocin is a peptide hormone secreted by the posterior pituitary that participates in labor and delivery and elicits milk ejection in lactating women. During the second half of pregnancy, uterine smooth muscle shows an increase in the expression of oxytocin receptors and becomes increasingly sensitive to the stimulant action of endogenous oxytocin. Pharmacologic concentrations of oxytocin powerfully stimulate uterine contraction. 

Oxytocin also causes contraction of myoepithelial cells surrounding mammary alveoli, which leads to milk ejection. 

OXYTOCIN. A polypeptide hormone which is secreted by the posterior lobe of the pituitary gland of mammals and other vertebrates. Oxytocin exerts a stimulating effect upon the muscles of the breast (milk-ejection) and those of the uterus of mammals. It is sometimes used medically to stimulate labor in cases of difficult childbirth and to time the onset of labor. 

Posterior lobe Antidiuretic hormone [ADH] Oxytocin T renal reabsorption of water t uterine contraction t milk ejection during lactation... 

Oxytocin alters transmembrane ionic currents in myometrial smooth muscle cells to produce sustained uterine contraction. The sensitivity of the uterus to oxytocin increases during pregnancy. Oxytocin-induced myometrial contractions can be inhibited by 13-adrenoceptor agonists, magnesium sulfate, or inhalation anesthetics. Oxytocin also causes contraction of myoepithelial cells surrounding mammary alveoli, which leads to milk ejection. Without oxytocin-induced contraction, normal lactation cannot occur. Oxytocin has weak antidiuretic and pressor activity. 

Impaired milk ejection may respond to nasal oxytocin. Synthetic peptide and nonpeptide oxytocin antagonists that can prevent premature labor are being investigated. 

Oxytocin causes contraction of the uterine smooth muscles and stimulates milk ejection in the lactating glands. 

Oxytocin is reflexly released from the pituitary following suckling (also by manual stimulation of the nipple) and causes almost immediate contraction of the myoepithelium of the breast it can be used to enhance milk ejection (nasal spray). The only other clinically important effect is on the blood pressure, which may fall if an overdose is given. 

Oxytocin may be used to facilitate the contraction of the mammary alveolar myoepithelial cells and thus promote milk ejection. After the mammary gland has been emptied manually, i.v. oxytocin (20 lU) will allow the additional collection of milk from lactating mares. 

It regulates reproductive functions. In humans it has a definitive role, with oxytocin, in lactation and milk ejection. In animals, it has a wide range of roles in reproduction, electrolyte balance, growth and development of the young. 

Oxytocin is a nonapeptide secreted by the magnicellular neurons of the hypothalamus and stored in the neurohypophysis along with AVP. It promotes uterine contractions and milk ejection and contributes to the second stage of labor. 

Touch receptors in nipple Ascending touch pathways (As above) Oxytocin Mammary gland milk ejection... 

Oxytocin Parturition Suckling Uterine contraction Milk ejection... 

Oxytocin (e.g., Pitocin) T force and frequency of uterine contractions. Most pronounced in near-term uterus. Contraction of myoepithelium surrounding alveoli of mammary gland. Antidiuretic (vasopressin) effects. Drug of choice to induce or accelerate labor, to decrease postpartum uterine bleeding. Stimulates milk ejection from breast (nasal spray). ... 

The heart, as an endocrine organ itself, secretes the atrial natriuretic peptide, which has several important influences on the cardiovascular system. In addition to atrial natriuretic peptide, catecholamines, thyroid hormones, mineralocorticoids, sex steroids, and angiotensin II are other hormones also known to exert their effects on the cardiovascular functions and blood pressure. Hormones regulate the contraction and dilatation of the vascular bed. They may also affect the contraction of other smooth muscles other than the vascular smooth muscle. Oxytocin stimulates contraction of the myoepithelium in the mammary gland that is necessary for milk ejection. 

In addition to these trophic hormones, the pituitary is also responsible for the production of vasopressin (ADH) and oxytocin. Vasopressin is produced (or not) in response to the osmotic balance so that, if necessary, water reabsorption in the kidney is promoted, resulting in a more concentrated urine. Oxytocin is a hormone of pregnancy, associated both with uterine contraction in childbirth and milk ejection in breast-feeding. 

Consider, for example, the milk-ejection reflex. This behavior may not normally be triggered by pheromones, but it can occur within seconds of the onset of suckling or exposure to stimuli, including odors, that have become associated with suckling (Wakerly, Clarke, Summerlee, 1994). Milk ejection in these circumstances would therefore seem to qualify as a released response. But because milk ejection is secondary to the hormonal effects of oxytocin released from the posterior pituitary, the response would seem to qualify as a primed effect. 

Oxytocin a neurohypophysial, peptide hormone, M, 1,007. O. causes contraction of the smooth muscle of the uterus and of the mammary gland (milk ejection). It is structurally related to the other neurohypophysial hormone. Vasopressin (see) these two hormones have a common ancestry and there is an overlap in their physiological activities. In lower vertebrates, four other neurohypophysial hormones have... 

Oxytocin (D 23) Vertebrates (Pituitary gland) Stimulates milk ejection in mammals... 

Oxytocin Polypeptide Posterior pituitary Uterus and mammary glands Contraction of smooth muscle. Milk ejection... 

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