The role of brain serotonin (5-hydroxytryptamine, 5-HT) in the control of LH, FSH and prolactin secretion was studied in two groups of experimental animals: intact adult male rats and ovariectomized adult female rats. 5-Hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, and fluoxetine, a specific inhibitor of 5-HT uptake, were given either alone or together. 5\ x =r eq-\ Hydroxytryptophan (50 mg/kg) was administered intraperitoneally and fluoxetine (20 \g=m\g/rat) was given into one of the lateral ventricles of the brain. Neither 5-HTP nor fluoxetine given alone affected LH secretion but combined treatment with the two drugs elicited a significant increase in serum LH levels in both intact male and ovariectomized female rats. Fluoxetine and 5-HTP, alone or together, did not modify FSH secretion in either kind of animal. In intact males and in ovariectomized females, 5-HTP induced a significant increase in prolactin release; fluoxetine alone was ineffective. In male animals treated with fluoxetine plus 5-HTP, serum prolactin levels increased but such an increase was lower than that found in the animals treated only with 5-HTP. In ovariectomized rats, the combined treatment induced an increase in serum prolactin levels similar to that found in animals treated with 5-HTP alone.These data suggested that brain serotonin exerts a stimulating effect on LH secretion in both intact male and ovariectomized rats, but that it does not play any role in the control of FSH release in either kind of animal and that central serotoninergic pathways participate in the stimulating control of prolactin release from the anterior pituitary gland. However, some of the data also suggested the possibility of the existence in the brain of serotoninergic systems inhibiting prolactin secretion.

No abstract

Continuous light (CL) induces constant estrous anovulatory (CEA) syndrome and blockade of pineal gland activity. Chronic treatment with metatonin is able to overcome the anovulatory state in about 70% of CL-CEA rats, and the luteinizing effect of melatonin is significantly counteracted either by feeding the animals with a tryptophan-poor diet or by injecting methiothepin, a blocker of central serotoninergic receptors. It appears that melatonin elicits luteinization in CL-CEA rats through the brain serotoninergic system.

No abstract

No abstract