title: Different effects of baclofen on LH and cortisol responses to naloxone in normal men.
abstract: The possible involvement of GABAergic B receptors in the control of LH and ACTH/cortisol secretion in response to naloxone was evaluated in seven normal men. Subjects were tested with naloxone (4 mg IV bolus plus 10 mg infused over 2 hr) with or without previous treatment with the gamma-aminobutyric acid (GABA)-ergic B receptor agonist, baclofen (5, 10 or 15 mg PO 30 min before naloxone). In additional experiments, six normal men were tested with 15 mg baclofen or placebo 30 min before a 2-hr infusion of normal saline. Plasma cortisol levels rose 70% in response to naloxone. The naloxone-induced cortisol rise was not modified by pretreatment with baclofen (5, 10 or 15 mg). Plasma LH concentrations rose 66% in response to naloxone. When the lowest dose of baclofen (5 mg) was administered, the LH response to naloxone remained unchanged. In contrast, 10 mg baclofen produced a significant reduction, and 15 mg baclofen completely abolished the naloxone-induced LH rise. The administration of baclofen or placebo alone did not change basal plasma levels of cortisol and LH. These data suggest that, in normal men, GABA B receptors participate in the endogenous opioidergic control of LH secretion, but not of ACTH/cortisol secretion.
authors.affiliation: Institute of Internal Medicine, School of Medicine, University of Parma, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Coiro
authors.forename: R
authors.initials: R
authors.lastname: Volpi
authors.forename: A
authors.initials: A
authors.lastname: Marcato
authors.forename: P
authors.initials: P
authors.lastname: Bertoni
authors.forename: U
authors.initials: U
authors.lastname: Cavazzini
authors.forename: G
authors.initials: G
authors.lastname: Caffarri
authors.forename: L
authors.initials: L
authors.lastname: Capretti
authors.forename: G
authors.initials: G
authors.lastname: Rossi
authors.forename: P
authors.initials: P
authors.lastname: Chiodera
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D001418:Baclofen / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D011292:Premedication; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D012016:Reference Values
chemical_list: D011963:Receptors, GABA-A; D009270:Naloxone; D000324:Adrenocorticotropic Hormone; D007986:Luteinizing Hormone; D001418:Baclofen; D006854:Hydrocortisone