Prolactin release-inhibiting hormone

Prolactin release-inhibiting hormone or factor, prolactostatin. 

Prolactostatin, prolactin release-inhibiting hormone, PRIH or PIH, prolactin release-inhibiting factor, PRIF, a hypothalamic substance of (until now) unknown structure that inhibits the release of prolactin. 

PIH acronym of prolactin release inhibiting hormone (see Releasing hormones). 

Prolactin release Inhibiting hormone see Releasing hormones. 

Prolactin releasing factor (PRF), prolactin releasing hormone, prolactoliberin a hormone thought to be identical with thyrotropin releasing factor, llie structure of Prolactin release inhibiting hormone (PIH) (prolactostatin) is unknown. PRF promotes, whereas PIH inhibits the synthesis and secretion of prolaction by the anterior pituitary. 

Prolactin inhibiting factor (mammals) PIF Prolactin release inhibiting hormone PRIH... 

Prolactin (PRL) Protein, MW 20,000 Prolactin release factor (PRF) may or may not be identical to thyrotropin-releasing hormone Prolactin release-inhibiting factor (PIF) most likely dopamine Supports lactation... 

Statins, release inhibiting factors, release inhibiting hormones, neurohormones synthesized in the small-cell region of the hypothalamus and transported via the bloodstream to the anterior pituitary. Members of the statins include melanostatin, somatostatin, and prolactostatin. They inhibit the secretion of melanotropin, somatotropin, and prolactin, respectively. Together with the corresponding liberins, the statins regulate the levels of the three pituitary hormones. 

A polypeptide hormone secreted by the anterior pituitary gland in both males and females. The highest serum levels occur in pregnancy, when, along with other hormones, it promotes lactation and mammary gland growth. Prolactin secretion, unlike other pituitary hormones, is limited by a hypothalamic prolactin-release inhibiting factor (PIF). 

The release of prolactin from the adenohypophysis is normally inhibited by prolactin-inhibiting hormone (PIH, dopamine) from the hypothalamus. Prolactin secretion is also controlled by prolactin-releasing factor (PRF). The release of PRF from the hypothalamus is mediated by reflexes elicited by suckling and breast stimulation. 

Rettori V, Wenger T, Snyder G, Dalterio S, McCann SM. (1988). Hypothalamic action ofdelta-9-tetrahydrocannabinol to inhibit the release of prolactin and growth hormone in the rat. Neuroendocrinology. 47(6) 498-503. 

The dopamine D2 agonists bromocriptine and cabergoline (pp. 114, 188) inhibit prolactin-releasing AH cells (indications suppression of lactation, prolactin-producing tumors). Excessive, but not normal, growth hormone release can also be inhibited (indication acromegaly) (3). 

Endocrine system Morphine and other opioid analgesics stimulate the release of vasopressin and prolactin and inhibit the release of luteinizing hormone, ACTH and follicle stimulating hormone. 

Endocrine system Dopamine inhibits prolactin release in human being. It also acts on somatotrophs to increase growth hormone release. 

A 56-residue peptide, which is formed from the 10-kDa precursor to GnRH, inhibits secretion of prolactin.75 Inhibition of FSH release is accomplished by feedback inhibition. Hormones known as inhibins are produced in the gonads and act to inhibit release of FSH from the pituitary.76... 

The role of cyclic AMP as modulator of prolactin secretion was first suggested by the finding of a stimulatory effect of cyclic AMP derivatives (17-22) and inhibitors of cyclic nucleotide phosphodiesterase activity such as theophylline and IBMX (22-26) on the secretion of this hormone. More convincing evidence supporting a role of cyclic AMP in the action of dopamine on prolactin secretion had to be obtained, however, by measurement of adenohypophysial adenylate cyclase activity or cyclic AMP accumulation under the influence of the catecholamine. As illustrated in Fig. 1, addition of 100 nM dopamine to male rat hemipituitaries led to a rapid inhibition of cyclic AMP accumulation, a maximal effect (30% inhibition) being already obtained 5 min after addition of the catecholamine. Thus, while dopamine is well known to stimulate adenylate cyclase activity in the striatum (27, 28), its effect at the adenohypophysial level in intact cells is inhibitory. Dopamine has also been found to exert parallel inhibitory effects on cyclic AMP levels and prolactin release in ovine adenohypophysial cells in culture (29) and purified rat mammotrophs (30). Using paired hemipituitaries obtained from female rats, Ray and Wallis (22) have found a rapid inhibitory effect of dopamine on cyclic AMP accumulation to approximately 75% of control. 

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