title: Leptin increases luteinizing hormone secretion of fasting female rats.
abstract: OBJECTIVE
  To investigate whether leptin acts directly on the anterior hypophysis by influencing gonadotropin secretion in vivo.
  
  
  METHODS
  Cycling female rats were catheterised for frequent blood sampling and were either fasted or allowed free access to food. Stereotactic lesion of the medial preoptic area (MPOA) of the hypothalamus was performed in order to eliminate gonadotropin releasing hormone (GnRH) production. Leptin was administered at a dose of one mg/kg i.v. and blood samples were taken just before leptin administration and then after 30, 60, 90, 120, and 180 minutes. Plasma gonadotropin levels were determined. With completion of sampling, the brains were removed and the localisation of the lesions was verified histologically.
  
  
  RESULTS
  Leptin at one mg/kg induced an increase in luteinizing hormone (LH) secretion in fasting rats, both in those with a lesion and those with intact medial preoptic area with a peak occurring 90 minutes after infusion. The augmenting effect was more prominent when the hypothalamus was intact. There was no effect in fed animals with or without lesion. Similarly, no effect was observed on follicle stimulating hormone (FSH) levels in any of the experimental groups.
  
  
  CONCLUSIONS
  Leptin acts directly on the hypophysis enhancing LH but not FSH secretion. Nutritional state influences leptin's effect on the hypothalamus and the hypophysis.
authors: T
authors: T
authors: Dagklis
authors: D
authors: D
authors: Kouvelas
authors: K
authors: K
authors: Kallaras
authors: G
authors: G
authors: Papazisis
authors: S
authors: S
authors: Petousis
authors: C
authors: C
authors: Margioula-Siarkou
authors: P
authors: P
authors: Skepastianos
authors: B C
authors: BC
authors: Tarlatzis
mesh_terms: D000818:Animals; D005215:Fasting / Q000378:metabolism*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D020738:Leptin / Q000008:administration & dosage / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood*; D010902:Pituitary Gland / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D020738:Leptin; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone