title: Naloxone does not modify fenfluramine-induced prolactin increase in obese patients.
abstract: OBJECTIVE
  To evaluate whether the supposed physiological interaction between serotoninergic and opioidergic pathways in the modulation of PRL release is preserved in human obesity, a pathological condition in which these two systems are greatly impaired.
  
  
  METHODS
  According to a single-blind randomized procedure, three tests were performed: test A (oral placebo + saline infusion over 5 hours), test B (fenfluramine, a well known serotoninergic drug, 60 mg orally + saline infusion over 5 hours) and test C (fenfluramine at the same dose + naloxone, an opiate receptor antagonist, infusion over 5 hours at a dose of 3 mg/h).
  
  
  METHODS
  Ten obese women (body mass index 34.4 +/- 2.3 kg/m2, mean +/- SE) and ten normal-weight sex and age-matched subjects (body mass index 22.3 +/- 2.4 kg/m2) volunteered for the study.
  
  
  METHODS
  At each test, blood samples for PRL determination were collected in basal conditions (time 0) and every hour for 5 hours. Plasma PRL was determined by radioimmunoassay.
  
  
  RESULTS
  In controls, naloxone significantly reduced the clear-cut PRL increase induced by fenfluramine. In obese patients, serotoninergic stimulation caused an increment in PRL levels similar to that in the controls, but opioid receptor blockade by naloxone did not affect this response.
  
  
  CONCLUSIONS
  These findings confirm that there is a physiological relationship between the serotoninergic and the opioidergic systems in the control of PRL secretion and show that this interaction is not present in obese subjects. Our data provide indirect proof of the functional impairment of these two systems in human obesity.
authors.affiliation: Fisiopatologia Endocrina, Clinica Medica 1a, University of Pisa, Italy.
authors.forename: G F
authors.initials: GF
authors.lastname: Argenio
authors.forename: G P
authors.initials: GP
authors.lastname: Bernini
authors.forename: M S
authors.initials: MS
authors.lastname: Vivaldi
authors.forename: C
authors.initials: C
authors.lastname: del Corso
authors.forename: R
authors.initials: R
authors.lastname: Santoni
authors.forename: F
authors.initials: F
authors.lastname: Franchi
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005277:Fenfluramine / Q000494:pharmacology*; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology*; D009765:Obesity / Q000097:blood / Q000503:physiopathology*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D016037:Single-Blind Method
chemical_list: D005277:Fenfluramine; D009270:Naloxone; D011388:Prolactin