Estrogen improves performance of reinforced T-maze alternation and prevents the amnestic effects of scopolamine administered systemically or intrahippocampally.
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.
Fader
A J
AJ
Department of Psychology, Tulane University, New Orleans, Louisiana, 70118, USA.
Hendricson
A W
AW
Dohanich
G P
GP
D000704:Analysis of Variance; D000818:Animals; D004958:Estradiol / Q000494:pharmacology* / Q000502:physiology*; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D018782:Maze Learning / Q000187:drug effects*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D008569:Memory Disorders / Q000139:chemically induced / Q000503:physiopathology; D010052:Ovariectomy; D051381:Rats; D011919:Rats, Inbred Strains; D012601:Scopolamine / Q000037:antagonists & inhibitors
D004958:Estradiol; D012601:Scopolamine