title: Influence of different estrogens on neuroplasticity and cognition in the hippocampus.
abstract: BACKGROUND
  Estrogens modulate the morphology and function of the hippocampus. Recent studies have focused on the effects of different types of estrogens on neuroplasticity in the hippocampus and cognition. There are three main forms of estrogens found in mammals: estradiol, estrone, and estriol. The vast majority of studies have used estradiol to investigate the effects of estrogens on the brain.
  
  
  METHODS
  This review focuses on the effects of different estrogens on adult hippocampal neurogenesis, synaptic plasticity in the hippocampus, and cognition in female rats.
  
  
  CONCLUSIONS
  Different forms of estrogens modulate neuroplasticity and cognition in complex and intriguing ways. Specifically, estrogens upregulate adult hippocampal neurogenesis (via cell proliferation) and synaptic protein levels in the hippocampus in a time- and dose-dependent manner. Low levels of estradiol facilitate spatial working memory and contextual fear conditioning while high levels of estradiol impair spatial working, spatial reference memory and contextual fear conditioning. In addition, estrone impairs contextual fear conditioning.
  
  
  CONCLUSIONS
  Advances in our knowledge of how estrogens exert their effects on the brain may ultimately lead to refinements in targeted therapies for cognitive impairments at all stages of life. However caution should be taken in interpreting current research and in conducting future studies as estrogens likely work differently in males than in females.
authors.affiliation: Department of Psychology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Cindy K
authors.initials: CK
authors.lastname: Barha
authors.forename: Liisa A M
authors.initials: LA
authors.lastname: Galea
mesh_terms: D000818:Animals; D003071:Cognition / Q000187:drug effects / Q000502:physiology*; D004958:Estradiol / Q000378:metabolism* / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D008297:Male; D055495:Neurogenesis / Q000187:drug effects / Q000502:physiology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D012727:Sex Characteristics
chemical_list: D004967:Estrogens; D004958:Estradiol