Estrogen improves performance of reinforced T-maze alternation and prevents the amnestic effects of scopolamine administered systemically or intrahippocampally

Neurobiol Learn Mem. 1998 May;69(3):225-40. doi: 10.1006/nlme.1998.3820.


In a previous study, administration of high doses of estradiol benzoate (100 microgram/kg for 3 days im) to ovariectomized Long-Evans rats counteracted impairments of reinforced T-maze alternation induced by systemic administration of scopolamine, a muscarinic receptor blocker. In the current study, daily administration of lower doses of estradiol benzoate (5 microgram/kg for 3 weeks sc) increased the number of correct reinforced alternations during T-maze acquisition in ovariectomized rats compared to oil-treated controls and prevented impairments of reinforced alternation induced by injection of scopolamine hydrobromide (0.2 mg/kg ip). Furthermore, scopolamine (20 microgram) delivered bilaterally to the dorsal hippocampus reduced reinforced T-maze alternation in ovariectomized rats previously trained to complete this task while daily treatment with estradiol benzoate (5 microgram/kg sc) for 1 week prior to scopolamine infusion counteracted this impairment. In summary, physiological levels of estrogen improved performance during acquisition of reinforced T-maze alternation and prevented impairments induced by scopolamine administered systemically or intrahippocampally.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Analysis of Variance
  • Animals
  • Estradiol / pharmacology*
  • Estradiol / physiology*
  • Female
  • Hippocampus / drug effects
  • Hippocampus / physiology*
  • Maze Learning / drug effects*
  • Memory / drug effects
  • Memory / physiology*
  • Memory Disorders / chemically induced
  • Memory Disorders / physiopathology
  • Ovariectomy
  • Rats
  • Rats, Inbred Strains
  • Scopolamine / antagonists & inhibitors


  • Estradiol
  • Scopolamine