The effects of Type I and Type II corticosteroid receptor agonists on exploratory behavior and spatial memory in the Y-maze |
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Authors: | Cheryl D Conrad Sonia J Lupien Leila C Thanasoulis Bruce S McEwen |
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Institution: | aLaboratory of Neuroendocrinology, Box 165, Rockefeller University, 1230 York Avenue, New York, NY 10021, USA;bDouglas Hospital Research Center-McGill University, 6875 Boulevard Lasalle, Montréal, Qué. H4H 1R3, Canada |
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Abstract: | We investigated the effects of two adrenal steroid agonists on adrenalectomized (ADX) rats' performance on the Y-maze. The Y-maze was chosen because memory can be assessed quickly and because it is sensitive to various parameters of exploratory behavior and spatial memory performance. Four days after surgery, ADX rats were injected with aldosterone (ALDO, a selective Type I receptor agonist), RU362 (a selective Type II receptor agonist) or sesame vehicle at three different time points (120 min prior to Trial 1, immediately after Trial 1 or 120 min after Trial 1). SHAM-operated rats injected with vehicle were also tested. The results indicate that vehicle-treated ADX rats were impaired on spatial recognition memory compared to SHAM rats. Treatment with ALDO restored spatial recognition memory performance of ADX rats to a level comparable to SHAM-treated rats by acting on acquisition and consolidation, whereas treatment with RU362 did not change the poor spatial recognition memory performance of ADX rats. Discrimination memory was improved only when either agonist was injected prior to the first trial, strongly suggesting a non-selective effect of corticosteroids on discrimination memory such as increasing arousal. A detailed analysis of exploratory behavior showed that both the ALDO- and RU362-treated rats explored the Y-maze more than the ADX and SHAM groups at all periods of the experiment. These results show that the non-specific increase in exploratory behavior induced by replacing corticosteroids targeted at Type I and Type II receptors was used differentially with the ALDO-treated rats learning and consolidating spatial information better than the RU362-treated rats. These data are discussed along with other evidence to suggest that Type II receptors may require the simultaneous occupancy of Type I receptors to affect learning and memory processes. |
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Keywords: | Learning Adrenal steroid Aldosterone Type I receptor Type II receptor Spatial recognition memory Discrimination memory |
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