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Pituitary prolactin secretion is regulated by endocrine neurons in the hypothalamus. The most important of these are the neurosecretory tuberoinfundibulum (TIDA) neurons of the arcuate nucleus that secrete dopamine (a.k.a. Prolactin Inhibitory Hormone) to act on the D 2 receptors of lactotrophs, causing inhibition of prolactin secretion.
The arcuate nucleus and the periventricular nucleus of the hypothalamus have dopamine neurons that form an important projection—the tuberoinfundibular pathway which goes to the pituitary gland, where it influences the secretion of the hormone prolactin. [50] Dopamine is the primary neuroendocrine inhibitor of the secretion of prolactin from ...
Dopamine released at this site inhibits the secretion of prolactin from anterior pituitary gland lactotrophs by binding to dopamine receptor D2. Some antipsychotic drugs block dopamine in the tuberoinfundibular pathway, which can cause an increase in the amount of prolactin in the blood (hyperprolactinemia).
Prolactin secretion in the pituitary lactrotroph cells is normally suppressed by the brain chemical dopamine, which binds to dopamine receptors. Drugs that block the effects of dopamine at the pituitary or deplete dopamine stores in the brain may cause the pituitary to secrete excess prolactin without an inhibitory effect.
The dopamine neurons of the dopaminergic pathways synthesize and release the neurotransmitter dopamine. [2] [3] Enzymes tyrosine hydroxylase and dopa decarboxylase are required for dopamine synthesis. [4] These enzymes are both produced in the cell bodies of dopamine neurons. Dopamine is stored in the cytoplasm and vesicles in axon terminals.
Dopamine released from their nerve endings at the median eminence is transported to the anterior pituitary gland, where it regulates the secretion of prolactin. Dopamine inhibits prolactin secretion, so when the TIDA neurons are inhibited, there is increased secretion of prolactin, which stimulates lactogenesis (milk production).
Prolactin inhibitors are mainly used to treat hyperprolactinemia (high prolactin levels). [1] Agonists of the dopamine D 2 receptor such as bromocriptine and cabergoline are able to strongly suppress pituitary prolactin secretion and thereby decrease circulating prolactin levels, and so are most commonly used as prolactin inhibitors. [1]
A prolactin cell (also known as a lactotropic cell, epsilon acidophil, lactotrope, lactotroph, mammatroph, mammotroph) is a cell in the anterior pituitary which produces prolactin (a peptide hormone) in response to hormonal signals including dopamine (which is inhibitory), thyrotropin-releasing hormone and estrogen (especially during pregnancy), which are stimulatory.