title: Food restriction-induced augmentation of heroin seeking in female rats: manipulations of ovarian hormones.
abstract: BACKGROUND
  Food restriction augments heroin seeking in chronically food-restricted male rats under withdrawal, an effect not yet examined in female rats. Importantly, women and female rats possess an increased vulnerability to drugs of abuse, which may be mediated by fluctuations in ovarian hormones.
  
  
  OBJECTIVE
  We investigated the role of estradiol and progesterone in augmented heroin seeking in chronically food-restricted female rats, under withdrawal.
  
  
  METHODS
  Female rats self-administered heroin for 10-12 days and were then allowed unrestricted (sated) or restricted access to food (FDR; ∼10 % reduction in body weight) for 14 days. On day 14, rats underwent a heroin-seeking test. Exp. 1: Rats underwent ovariectomy or sham surgery and were treated with a low dose of estradiol (5.0 % in cholesterol; subcutaneous capsule). Exp. 2: Rats underwent ovariectomy and were administered with a high dose of estradiol (0.5 mg/kg; subcutaneous) for 8 days before testing. Exp. 3: Progesterone injections (2.0 mg/kg; subcutaneous) were administered 24 h and 2 h before testing.
  
  
  RESULTS
  Food restriction resulted in augmented heroin seeking, compared to sated controls. While ovariectomy had no effect, estradiol replacement attenuated the food restriction effect. Injections of progesterone had no effect on heroin seeking in either the sated or FDR groups.
  
  
  CONCLUSIONS
  The effect of food restriction on heroin seeking in female rats under withdrawal is as robust as previously found in males. Interestingly, estradiol replacement, but not progesterone, attenuates the food restriction effect in the ovariectomized rats, possibly due to its anorexic properties.
authors.affiliation: Department of Psychology, Center for Studies in Behavioral Neurobiology/Groupe de Recherche en Neurobiologie Comportementale, Concordia University, Montreal, Quebec, Canada.
authors.forename: Firas
authors.initials: F
authors.lastname: Sedki
authors.forename: James
authors.initials: J
authors.lastname: Gardner Gregory
authors.forename: Adriana
authors.initials: A
authors.lastname: Luminare
authors.forename: Tracey M
authors.initials: TM
authors.lastname: D'Cunha
authors.forename: Uri
authors.initials: U
authors.lastname: Shalev
mesh_terms: D000818:Animals; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood*; D005260:Female; D005508:Food Deprivation / Q000502:physiology*; D003932:Heroin / Q000008:administration & dosage*; D006556:Heroin Dependence / Q000097:blood* / Q000523:psychology; D010052:Ovariectomy; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D011374:Progesterone / Q000008:administration & dosage / Q000097:blood*; D051381:Rats; D012646:Self Administration
chemical_list: D011374:Progesterone; D004958:Estradiol; D003932:Heroin