Increased Prolactin produces sensitivity and puffy nipples, from that areola expansion occurs. Up-regulate a prolactin source. Fenugreek is usually suggested. Dopamine turns of the Prolactin signal. Prolactin down regulate estrogen, progesterone too.
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Prolactin will increase breast sensitivity, and stimulation will increase more prolactin, which will reduce E. The nipples and areola respond to this stimulation by enlarging and becoming more prominent and developing more nerve endings. Nipple stimulation sends a signal to the pituitary to release prolactin. Too much stimulation turns off it off though.
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Dopamine serves as the major prolactin-inhibiting factor or brake on prolactin secretion. Dopamine is secreted into portal blood by hypothalamic neurons, binds to receptors on lactotrophs, and inhibits both the synthesis and secretion of prolactin. Agents and drugs that interfere with dopamine secretion or receptor binding lead to enhanced secretion of prolactin.
In addition to tonic inhibition by dopamine, prolactin secretion is positively regulated by several hormones, including thyroid-releasing hormone, gonadotropin-releasing hormoneand vasoactive intestinal polypeptide. Stimulation of the nipples and mammary gland, as occurs during nursing, leads to prolactin release. This effect appears to be due to a spinal reflex arc that causes release of prolactin-stimulating hormones from the hypothalamus.
Estrogens provide a well-studied positive control over prolactin synthesis and secretion. The increasing blood concentrations of estrogen during late pregnancy appear responsible for the elevated levels of prolactin that are necessary to prepare the mammary gland for lactation at the end of gestation.
http://www.vivo.colostate.edu/hbooks/pat...actin.html