title: Hypothalamic Ghrelin suppresses pulsatile secretion of luteinizing hormone via beta-endorphin in ovariectomized rats.
abstract: OBJECTIVE
  Ghrelin, an endogenous growth hormone secretagogue, is a known accelerator of feeding behavior and suppresses pulsatile secretion of luteinizing hormone (LH) in ovariectomized rats. However, the mechanisms underlying this action remain unclear. We examined the effects of naloxone (NAL), a specific opioid antagonist, on the suppression of pulsatile LH secretion by ghrelin to determine whether beta-endorphin (beta-END) is involved in this suppressive effect.
  
  
  METHODS
  Ghrelin was administered intracerebroventricularly, and NAL was injected intravenously in ovariectomized rats; then, serum LH concentrations were measured by radioimmunoassay in blood samples drawn every 6 min for 2 h to analyze pulsatile secretion.
  
  
  RESULTS
  Administration of ghrelin significantly reduced mean LH concentration and pulse frequency. Coadministration of NAL with ghrelin significantly restored mean LH concentration and pulse frequency.
  
  
  CONCLUSIONS
  Suppressive effect of intracerebroventricular injection of ghrelin on pulsatile LH secretion was mediated by beta-END, suggesting that hypothalamic ghrelin suppressed pulsatile gonadotropin-releasing hormone secretion via beta-END in female rats.
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan. r-ogata @ pop21.odn.ne.jp
authors.forename: Rie
authors.initials: R
authors.lastname: Ogata
authors.forename: Toshiya
authors.initials: T
authors.lastname: Matsuzaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwasa
authors.forename: Machiko
authors.initials: M
authors.lastname: Kiyokawa
authors.forename: Naoko
authors.initials: N
authors.lastname: Tanaka
authors.forename: Akira
authors.initials: A
authors.lastname: Kuwahara
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yasui
authors.forename: Minoru
authors.initials: M
authors.lastname: Irahara
mesh_terms: D000818:Animals; D001835:Body Weight; D002404:Catheterization; D005260:Female; D054439:Ghrelin / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010052:Ovariectomy; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D001615:beta-Endorphin / Q000378:metabolism*
chemical_list: D054439:Ghrelin; D009292:Narcotic Antagonists; D009270:Naloxone; D001615:beta-Endorphin; D007986:Luteinizing Hormone