Thyrotropin-releasing Hormone (TRH) is a tropic hormone that stimulates release of thyroid-stimulating hormone (TSH) and prolactin.1 It binds to the human TRH receptor (TRHR) expressed in CHO cells and to rat TRHR in rat brain membranes (IC50s = 25 and 198 nM, respectively).2,3 TRH (1 μM) decreases polyphosphoinositide and increases arachidonic and oleic acid diacylglycerol incorporation into lipids of GH3 rat pituitary tumor cells.4 In vitro, it dose-dependently increases TSH release from rat anterior pituitary slices and prolactin release from cultured anterior pituitary cells.5,6 In vivo, TRH (0.01 mg/kg) increases TSH and prolactin plasma levels in rats.1
1.Dettmar, P.W., Lynn, A.G., Metcalf, G., et al.The ability of RX 77368 - a stabilised analogue of TRH - to provoke the secretion of prolactin and TSH in vivoNeuropeptides3(1)1-8(1982) 2.Yamada, M., Iwasaki, T., Satoh, T., et al.Activation of the thyrotropin-releasing hormone (TRH) receptor by a direct precursor of TRH, TRH-GlyNeurosci. Lett.196(1-2)109-112(1995) 3.Bhargava, H.N., and Das, S.Evidence for opiate action at the brain receptors for thyrotropin-releasing hormoneBrain Res.368(2)262-267(1986) 4.Martin, T.F.J.Thyrotropin-releasing hormone rapidly activates the phosphodiester hydrolysis of polyphosphoinositides in GH3 pituitary cells. Evidence for the role of a polyphosphoinositide-specific phospholipase C in hormone actionJ. Biol. Chem.258(24)14816-14822(1983) 5.Iriuchijima, T., Michimata, T., Miyashita, K., et al.Thyroid hormones regulate the formation of inositol phosphate in response to thyrotropin-releasing hormone in rat anterior pituitariesNeuropeptides21(1)49-53(1992) 6.Apfelbaum, M.E.Role of vasoactive intestinal peptide and 5-HT2 receptor subtype in serotonin stimulation of basal and thyrotropin-releasing-hormone-induced prolactin release in vitro from rat pituitary cellsNeuroendocrinology67(1)45-50(1998)