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 treatments would attenuate the effect of the muscarinic receptor blocker scopolamine on a memory task. Ovariectomized rats were trained first to alternate for food reward between the arms of a T maze. Following training, females treated with scopolamine hydrobromide (0.2 mg/kg ip) did not alternate correctly between the arms of the T maze and responded at chance levels. However, when estradiol benzoate (25 mu g) was administered 72, 48, and 24 hr before testing alone or in combination with progesterone (500 mu g) administered 4-6 hr before testing, females alternated successfully between the arms of the T maze following scopolamine administration. Results indicate that gonadal steroids can completely counteract the impairment of T maze performance induced by scopolamine in female rats.