ESTROGEN AND ESTROGEN-PROGESTERONE TREATMENTS COUNTERACT THE EFFECT OF SCOPOLAMINE ON REINFORCED T-MAZE ALTERNATION IN FEMALE RATS

The purpose of the experiments was to determine if steroid hormone tre atments would attenuate the effect of the muscarinic receptor blocker scopolamine on a memory task. Ovariectomized rats were trained first t o alternate for food reward between the arms of a T maze. Following tr aining, females treated with scopolamine hydrobromide (0.2 mg/kg ip) d id not alternate correctly between the arms of the T maze and responde d at chance levels. However, when estradiol benzoate (25 mu g) was adm inistered 72, 48, and 24 hr before testing alone or in combination wit h progesterone (500 mu g) administered 4-6 hr before testing, females alternated successfully between the arms of the T maze following scopo lamine administration. Results indicate that gonadal steroids can comp letely counteract the impairment of T maze performance induced by scop olamine in female rats.