Abstract
Fourteen sets of quadruplet, Long-Evans rats were divided accordingly; from each set of quadruplets two were ovariectomized and two were sham-operated at day one. At 21 days of age, the animals were weaned and placed three-four to a cage. At 60 days of age the rats were separated so that one ovariectomized and one sham-operated animal were placed in the enriched environmental condition, and one overiectomized and one sham animal were placed in the improverised environmental condition. At 90 days of age the brains were removed from anesthetized animals, and cortical thickness was measured on representative, transverse histological sections from the anterior (M), middle (Se), and posterior (V) regions of the cortex. Statistically significant cortical thickness changes were noted between the sham-operated enriched and improverished animals. The thickness of the cortex did not differ significantly between the ovariectomized enriched and sham-operated enriched animals except for one area. However, very significant differences in total cortical thickness did occur between the impoverished ovariectomized rats and the sham-operated littermates. That ovariectomy alone can increase cortical thickness has been shown. In the present experiments the ovariectomized rat may have increased its cortical dimensions before being placed in the enriched condition so that the effects of enrichments are not generally manifest. Perhaps, the cortex has already approached its ‘ceiling’ before being exposed to the enriched condition. A possible explanation for the marked changes between the ovariectomized impoverished rat and its sham-operated littermate is that the increased cortical thickness caused by ovariectomy cannot readily decrease in 30 days of impoverishment; whereas, the sham-operated impoverished rat's brain can decrease in thickness due to a lack of stimuli for a 30 day period.
Published Version
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