title: Regulation of NPY and α-MSH expression by estradiol in the arcuate nucleus of Wistar female rats: a stereological study.
abstract: OBJECTIVE
  Feeding behavior in both animals and humans is modulated by estrogens, as shown by the increased adiposity observed in women and rats upon the drop of estradiol levels at menopause. Estradiol action on food intake is mediated through its cognate receptors within several hypothalamic nuclei, namely the arcuate nucleus (ARN). The ARN contains two neuronal populations expressing peptides that exert opposing effects on the central control of feeding: the orexigenic neuropeptide Y (NPY) and the anorexigenic α-melanocyte-stimulating hormone (α-MSH).
  
  
  METHODS
  To understand the role played by estradiol in the modulation of food intake, we have used an animal model of cyclic 17β-estradiol benzoate (EB) administration and stereological methods to estimate the total number of neurons immunoreactive for NPY and α-MSH in the ARN of ovariectomized rats.
  
  
  RESULTS
  Present results show that the experimentally induced EB cyclicity prompted a decrease in food consumption and in body weight. Data also show that ovariectomy induced an increase in NPY expression and a decrease in α-MSH expression in the ARN that were reverted by EB administration. Conversely, EB blocked the expression of NPY and increased the synthesis of α-MSH in ARN neurons, without affecting the overall sum of NPY and α-MSH neurons.
  
  
  CONCLUSIONS
  These results suggest that estradiol affects food intake and, consequently, body weight gain, through an overriding mechanism superimposed in the physiological balance between both peptides in the ARN of female rats.
authors.affiliation: a Department of Natural Sciences , State University of Southwest of Bahia , Bahia , Brazil.|b Faculty of Medicine, Department of Anatomy , University of Porto , Porto , Portugal.|c Faculty of Medicine, Center for Health Technology and Services Research (CINTESIS) , University of Porto , Porto , Portugal.
authors.forename: Elce C C
authors.initials: EC
authors.lastname: Rebouças
authors.affiliation: b Faculty of Medicine, Department of Anatomy , University of Porto , Porto , Portugal.|c Faculty of Medicine, Center for Health Technology and Services Research (CINTESIS) , University of Porto , Porto , Portugal.|d Department of Sciences , Institute of Research and Advanced Training in Health Sciences and Technologies (IINFACTS) , Advanced Institute of Health Sciences-North (ISCS-N), CESPU, CRL , Gandra , Portugal.
authors.forename: Sandra
authors.initials: S
authors.lastname: Leal
authors.affiliation: b Faculty of Medicine, Department of Anatomy , University of Porto , Porto , Portugal.|c Faculty of Medicine, Center for Health Technology and Services Research (CINTESIS) , University of Porto , Porto , Portugal.
authors.forename: Susana I
authors.initials: SI
authors.lastname: Sá
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000187:drug effects*; D002452:Cell Count; D003270:Contraceptive Agents / Q000494:pharmacology*; D004435:Eating / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009478:Neuropeptide Y / Q000235:genetics / Q000378:metabolism*; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar; D013238:Stereotaxic Techniques; D013997:Time Factors; D000521:alpha-MSH / Q000235:genetics / Q000378:metabolism*
chemical_list: D003270:Contraceptive Agents; D009478:Neuropeptide Y; C074283:estradiol 3-benzoate; D004958:Estradiol; D000521:alpha-MSH
keywords: Arcuate nucleus; Estrogen; Immunohistochemistry; Neuropeptide Y; stereology; α-Melanocyte-stimulating hormone