17beta-estradiol and enriched environment accelerate cognitive recovery after focal brain ischemia

Eur J Neurosci. 2009 Mar;29(6):1215-24. doi: 10.1111/j.1460-9568.2009.06662.x.

Abstract

Cognitive impairments, including spatial memory and learning deficiencies, are common after ischemic stroke. Estrogen substitution improves cognitive functions in post-menopausal women and ovariectomized rodents, partially through induction of neuroplasticity in the hippocampal formation. Post-ischemic housing of male rats in an enriched environment (EE) improves functional outcome, without changing infarct volume. We hypothesized that 17beta-estradiol combined with an EE would accelerate cognitive recovery after focal brain ischemia in ovariectomized rats and that recovery would be related to altered expression of nerve growth factor-induced gene (NGFI)-A in the hippocampus. 17beta-estradiol or placebo pellets were implanted 6 h after transient middle cerebral artery occlusion. Two days later, rats were placed in an EE or a deprived environment (DE) for 6 weeks. At 5 weeks after middle cerebral artery occlusion, 17beta-estradiol-treated rats housed in an EE showed improvements in cognitive function (i.e. shorter latency and path in the Morris water maze task) compared with placebo-treated animals housed in an EE. Furthermore, beneficial effects on latency and path were observed when comparing EE-housed vs. DE-housed 17beta-estradiol-treated rats. When comparing 17beta-estradiol-treated EE-housed rats vs. placebo-treated DE-housed rats, pronounced effects on latency and path were observed. Infarct volumes did not differ between groups. 17beta-estradiol-treated EE-housed rats had significantly higher NGFI-A mRNA expression bilaterally in the cornu ammonis 1 region and in the ipsilateral dentate gyrus of the hippocampus, compared with placebo-treated EE-housed rats. In conclusion, 17beta-estradiol treatment combined with an EE improved recovery of cognitive function after experimental brain ischemia, putatively through the upregulation of NGFI-A in hippocampal subregions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Brain Infarction / drug therapy
  • Brain Infarction / etiology
  • Brain Ischemia / complications
  • Cognition Disorders / drug therapy*
  • Cognition Disorders / etiology
  • Cognition Disorders / nursing*
  • Cognition Disorders / pathology
  • Disease Models, Animal
  • Early Growth Response Protein 1 / genetics
  • Early Growth Response Protein 1 / metabolism
  • Environment*
  • Estradiol / blood
  • Estradiol / therapeutic use*
  • Estrogens / blood
  • Estrogens / therapeutic use*
  • Female
  • Functional Laterality / drug effects
  • Gene Expression Regulation / drug effects
  • Hippocampus / drug effects
  • Motor Activity / drug effects
  • Neuropsychological Tests
  • Ovariectomy / methods
  • Psychomotor Performance / drug effects
  • Rats
  • Rats, Sprague-Dawley
  • Reaction Time / drug effects
  • Recovery of Function / drug effects*
  • Recovery of Function / physiology
  • Sensation / drug effects
  • Time Factors
  • Vibrissae / drug effects
  • Vibrissae / innervation

Substances

  • Early Growth Response Protein 1
  • Egr1 protein, rat
  • Estrogens
  • Estradiol