Serotonin (5-HT) is a neurotransmitter and neuromodulator in both the central and peripheral nervous systems. 5-HT, a hormone with widespread functions, is produced from tryptophan and works in the sensory-motor, autonomic and peripheral nervous systems. It signals cells through a large family of cell receptors (5-HTRs), and helps control the release of prolactin (PRL) at the hypothalamic and brain stem levels.
The anterior pituitary contains 5-HT, yet the exact site of prolactin release at the pituitary level is unknown. 5-HT alters PRL, growth hormone (GH), ACTH and luteinizing hormone (LH) release. The release of PRL is at nanomolar doses of 5-HT and causes a rapid release of PRL by anterior pituitary cells.
The present study, of rats and cells in culture, is of anterior pituitary cell cultures and their release of prolactin as altered by estrogens, thyroid hormones, and prolactin receptors. The release of prolactin by 5-HT was greatly increased by estradiol (a potent form of estrogen) in cell culture.
Estrogen increases 5-HT receptors in the rat anterior pituitary, and in one of these receptors, 5-HTR4, stimulation causes the rapid release of PRL. A 5-HTR4 antagonist blocked the PRL release. This, however, does not seem to be the only receptor involved in sexual and reproductive functions. 5-HT does not need to be absorbed into the cells for the effect of PRL release to occur.
CONCLUSION: Serotonin (5-HT) plays a role in sexual and reproductive functions mediated by the pituitary release of prolactin (PRL). The release is enhanced by the presence of estrogen and the action is mediated by the 5-HTR4 receptors.
NOTE: 5-OH tryptophan and tryptophan are known precursors to the production of 5-HT. Elevated levels of prolactin are a risk factor for many cancers. Certain medications for depression elevate blood levels of prolactin and prolactin is known to have over three hundred functions. Dopamine also reduces the production of prolactin.
To read the author’s abstract of the article click on the link to the author’s title of the article above.