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Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology


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NeuroendocrinologyİLetters incl. Psychoneuroimmunology & Chronobiology,
ISSNİ0172ñ780X Copyrightİ©İ1998, 1999, 2000, 2001 NeuroendocrinologyİLetters

NEL VOL. 19 No. 4
ORIGINAL ARTICLE

1998; 19:190-201

 

Effect of Type 2 Adrenal Receptor Agonist RU28362 on the Radial Arm Maze Performance of Adrenalectomized Rats
by Paul R. Vaher & Bruce S. McEwen

Abstract:

The effect of the type 2 adrenal steroid receptor activation on spatial memory was evaluated. Adrenalectomized (ADX) rats were treated with RU28362, a specific type 2 receptor agonist, and tested on a task of spatial memory, the radial arm maze (RAM). Earlier studies in this series have shown that ADX causes lasting deficits in RAM performance without of marked loss of granule cell neurons in the dentate gyrus (DG). Sham, ADX, and ADX rats treated with RU28362 were tested on the RAM 4 times a week for 3 weeks. RU28362 was delivered by osmotic minipump (10 µg/hr for 7 days, s.c.). Intake of 3% saline was measured as an index of serum levels of adrenal steroids. ADX rats treated with RU28362 made fewer correct choices in the first eight visits and more errors in completing the task than sham and ADX controls for the first week of testing. The effect lasted for two weeks, one week beyond the supposed life of the pump, and was paralleled by the suppression of saline intake. Saline intake increased in RU28362 treated rats during the third week and was accompanied by a trend towards a reduction in the number of maze errors. While poorer maze performance was accompanied by a somewhat decreased saline intake in RU28362 treated rats, a correlation between saline intake and measures of choice accuracy was not shown. As in previous studies, ADX did not result in a high frequency of granule cell pyknosis or a reduction in cross sectional DO area. Measures of DO morphology were not correlated to behavioral performance. It was concluded that RU28362 further impaired spatial memory performance in ADX rats. Thus, the type 2 receptor works in opposition to the type 1 receptor which was shown in our earlier study to facilitate spatial memory function in ADX rats.

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