The differential sensitivity of the hypothalamic-hypophysial-ovarian axis to 5-hydroxytryptophan alters the secretion of estradiol

Serotonin [5-hydroxytryptamine (5-HT)] modulates ovarian function. The precursor of 5-HT, 5-hydroxytryptophan (5-HTP), has been used to treat depression. However, the effects of 5-HTP on ovarian and reproductive physiology remain unknown. In this research, we analysed the impact of 5-HTP on the monoaminergic system and its interactions with the reproductive axis and ovarian estradiol secretion when administered by distinct routes. Female rats 30 days of age were injected with 5-HTP i.p. (100 mg/kg), into the ovarian bursa (1.5 mu g/40 mu L) or into the median raphe nucleus (20 mu g/2.5 mu L) and were killed 60 or 120 min after injection. As controls, we used rats of the same age injected with vehicle (0.9% NaCl). Monoamine, gonadotrophin and steroid ovarian hormone concentrations were measured. The injection of 5-HTP either i.p. or directly into the ovarian bursa increased the concentrations of 5-HT and the metabolite 5-hydroxyindole-3-acetic acid in the ovary. For both routes of administration, the serum concentration of estradiol increased. After i.p. injection of 5-HTP, the concentrations of luteinizing hormone were decreased and follicle-stimulating hormone increased after 120 min. Micro-injection of 5-HTP into the median raphe nucleus increased the concentrations of 5-HT in the anterior hypothalamus and dopamine in the medial hypothalamus after 120 min. Our results suggest that the administration of 5-HTP either i.p. or directly into the ovarian bursa enhances ovarian estradiol secretion. What is the central question of this study?Does the route of administration of 5-hydroxytryptophan affect the synthesis of steroid sex hormones in prepubertal female rats?What is the main finding and its importance?The injection of 5-hydroxytryptophan either i.p. or directly into the ovarian bursa in prepubertal female rats stimulated the serotoninergic system of the reproductive axis. In turn, this increased the secretion of estradiol, a gonadal hormone that regulates sexual maturation and several physiological processes in females.

Automated summary

This study reveals that administration of 5-hydroxytryptophan (5-HTP) either intraperitoneally or directly into the ovarian bursa enhances the concentrations of 5-HT and its metabolite in the ovary, as well as the serum concentration of estradiol. These findings suggest that 5-HTP has a promoting effect on ovarian function.