title: Hyperphagia and increased meal size are responsible for weight gain in rats treated sub-chronically with olanzapine.
abstract: BACKGROUND
  Atypical antipsychotic-induced weight gain is a significant impediment in the treatment of schizophrenia.
  
  
  OBJECTIVE
  In a putative model of antipsychotic drug-induced weight gain, we investigated the effects of sub-chronic olanzapine on body weight, meal patterns, the expression of genes encoding for hypothalamic feeding-related neuropeptides and the contribution of hyperphagia to olanzapine-induced weight gain in rats.
  
  
  METHODS
  In experiment 1, female rats received either olanzapine (1 mg/kg, p.o.) or vehicle, twice daily for 7 days, while meal patterns were recorded. At the end of the treatment regimen, we measured the levels of hypothalamic messenger RNAs (mRNAs) encoding neuropeptide-Y (NPY), hypocretin/orexin (HCRT), melanin concentrating hormone and pro-opiomelanocortin. NPY and HCRT mRNA levels were also assessed in a separate cohort of female rats treated acutely with olanzapine (1 mg/kg, p.o.). In experiment 2, we investigated the effect of a pair-feeding paradigm on sub-chronic (1 mg/kg, p.o.) olanzapine-induced weight gain.
  
  
  RESULTS
  In experiment 1, sub-chronic olanzapine increased body weight, food intake and meal size. Hypothalamic neuropeptide mRNA levels were unchanged after both acute and sub-chronic olanzapine treatment. In experiment 2, the restriction of food intake to the level of vehicle-treated controls abolished the sub-chronic olanzapine-induced increase in body weight.
  
  
  CONCLUSIONS
  Hyperphagia mediated by drug-induced impairments in satiety (as evidenced by increased meal size) is a key requirement for olanzapine-induced weight gain in this paradigm. However, olanzapine-induced hyperphagia and weight gain may not be mediated via alterations in the expression of the feeding-related hypothalamic neuropeptides examined in this study.
authors.affiliation: Department of Psychology, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
authors.forename: Nima
authors.initials: N
authors.lastname: Davoodi
authors.forename: Mikhail
authors.initials: M
authors.lastname: Kalinichev
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Korneev
authors.forename: Peter G
authors.initials: PG
authors.lastname: Clifton
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000009:adverse effects*; D001569:Benzodiazepines / Q000008:administration & dosage / Q000009:adverse effects*; D004435:Eating / Q000502:physiology / Q000523:psychology*; D005260:Female; D006963:Hyperphagia / Q000139:chemically induced*; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology; D009478:Neuropeptide Y / Q000096:biosynthesis; D009479:Neuropeptides / Q000502:physiology; D000077152:Olanzapine; D000068797:Orexins; D011333:Pro-Opiomelanocortin / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D015430:Weight Gain / Q000187:drug effects*
chemical_list: D014150:Antipsychotic Agents; D047908:Intracellular Signaling Peptides and Proteins; D009478:Neuropeptide Y; D009479:Neuropeptides; D000068797:Orexins; D012333:RNA, Messenger; D001569:Benzodiazepines; D011333:Pro-Opiomelanocortin; D000077152:Olanzapine