In vivo and in vitro studies on the effect of the serotoninergic system on luteinizing hormone and luteinizing hormone-releasing hormone secretion in prepubertal and peripubertal female rats.
The present investigations were designed to assess the effect of the serotoninergic system on luteinizing hormone (LH) and LH-releasing hormone (LH-RH) secretion in female rats aged 14 and 30 days. The administration of 5-hydroxytryptophan (5-HTP; 75 mg/kg i.p.) increased hypothalamic serotonin (5-HT) concentrations in both age groups, and did not affect hypothalamic norepinephrine (NE) concentrations or release. Serum LH levels were raised by 5-HTP in 14-day-old, but not in 30-day-old rats. Basal and KCl- (28 mM) stimulated LH-RH release by incubated hypothalamic fragments was significantly enhanced when 5-HTP was injected previously to 14-day-old animals. In 30-day-old rats, 5-HTP treatment did not modify basal LH-RH release, and decreased the KCl-stimulated LH-RH output. Similarly, the addition of 5-HT (10(-7) M) to superfused hypothalamic fragments enhanced basal LH-RH release in 14-day-old rats and blocked the increment in LH-RH release evoked by KCl in 30-day-old rats. The present results show that in 14-day-old female rats, the serotoninergic system (activated in vivo by 5-HTP treatment, or in vitro by 5-HT addition) exerts a stimulatory effect on LH-RH, and thus, on LH release. On the contrary, in 30-day-old animals, stimulated LH-RH secretion was inhibited by 5-HT. Apparently, the hypothalamic NE system is not implicated in this response. The participation of this changing effect of 5-HT on LH-RH/LH release at the onset of puberty is postulated.
Departamento de Fisiologia, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
P
P
Arias
B
B
Szwarcfarb
D C
DC
de Rondina
S
S
Carbone
R
R
Sverdlik
J A
JA
Moguilevsky
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007986:Luteinizing Hormone / Q000378:metabolism*; D008781:Methyltyrosines / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000502:physiology*; D019805:alpha-Methyltyrosine
D008781:Methyltyrosines; D012701:Serotonin; D007987:Gonadotropin-Releasing Hormone; D019805:alpha-Methyltyrosine; D011189:Potassium Chloride; D007986:Luteinizing Hormone; D006916:5-Hydroxytryptophan