title: Periovulatory plasma prolactin response to gonadotropin-releasing hormone: role of endogenous opiates.
abstract: It has been previously shown that in normal women during the periovulatory period, prolactin (PRL) levels increase after the administration of nonspecific stimuli, such as growth hormone-releasing hormone or gonadotropin-releasing hormone (GnRH). In order to gain insight into the mechanism of this response, we have tested the effect of a naloxone infusion (1.6 mg/h) on the PRL response to GnRH in 5 normal females, aged 20-27 years, tested during the periovulatory period. Naloxone was administered starting 60 min before GnRH administration (100 micrograms as an i.v. bolus). Naloxone clearly blunted the PRL response (basal 10.7 +/- 1.7 ng/ml, peak 11.8 +/- 0.2 ng/ml at 30 min, versus: basal 9.0 +/- 0.5 ng/ml, peak 20.6 +/- 3.9 ng/ml at 45 min after GnRH alone; significance of difference between peaks: p less than 0.05). A secondary late increase of PRL levels was observed, reaching about 60% of basal levels at 120 min (16.8 +/- 2.6 ng/ml). These data indicate that periovulatory PRL dynamics are altered by naloxone administration and suggest a possible involvement of opioid peptides in the 'paradoxical' PRL response to GnRH in normal subjects.
authors.affiliation: Institut of Endocrinology, Catholic University School of Medicine, Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: De Marinis
authors.forename: A
authors.initials: A
authors.lastname: Mancini
authors.forename: C
authors.initials: C
authors.lastname: D'Amico
authors.forename: F
authors.initials: F
authors.lastname: Calabró
authors.forename: P
authors.initials: P
authors.lastname: Zuppi
authors.forename: C
authors.initials: C
authors.lastname: Fiumara
authors.forename: A
authors.initials: A
authors.lastname: Barini
mesh_terms: D000328:Adult; D004723:Endorphins / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D007986:Luteinizing Hormone / Q000097:blood; D009270:Naloxone / Q000008:administration & dosage; D010060:Ovulation / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D011388:Prolactin / Q000097:blood*
chemical_list: D004723:Endorphins; D007987:Gonadotropin-Releasing Hormone; D009270:Naloxone; D011374:Progesterone; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone