Effects of adrenalectomy and selective adrenal steroid receptor agonists on spatial memory performance and dentate gyrus morphology.
Item
-
Title
-
Effects of adrenalectomy and selective adrenal steroid receptor agonists on spatial memory performance and dentate gyrus morphology.
-
Identifier
-
AAI9605674
-
identifier
-
9605674
-
Creator
-
Vaher, Paul Richard.
-
Contributor
-
Victoria Luine
-
Date
-
1995
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Psychology, Psychobiology | Biology, Neuroscience
-
Abstract
-
Adrenalectomy (ADX) causes neuronal degeneration in the dentate gyrus (DG) of the hippocampus as early as 3 days after surgery and extensive granule cell loss 3 to 4 months later. Since lesion of the DG causes deficits in spatial memory performance, the effect of ADX on spatial memory was investigated. Rats were adrenalectomized and tested on a radial arm maze (RAM) shortly after adrenal removal. ADX resulted in impaired spatial memory performance which lasted for up to 71 days. The presence of accessory adrenal tissue was assessed by measuring serum levels of corticosterone (CORT) and daily intake of 3% saline. Saline consumption was higher in ADX rats and was negatively correlated to serum CORT (r = {dollar}-{dollar}0.85, p {dollar}<{dollar} 0.0018). Persistent deficits in RAM performance occurred without the marked presence of pyknosis or the reduction of DG size suggesting that adrenal hormones themselves exert an activational effect on spatial memory prior to pervasive degeneration of DG neurons. We next assessed the involvement of Type 1 and Type 2 adrenal steroid receptors in spatial memory function by treating ADX rats with selective receptor analogs. Type 1 and Type 2 adrenal steroid receptors were shown to have opposite effects on spatial memory function; Replacement of the type 1 receptor agonist, aldosterone, restored normal spatial memory function in ADX rats whereas the type 2 agonist, RU28362, further impaired spatial memory function. On this basis, we predict that the dose-response relationship between serum CORT and spatial memory performance is an inverted U-shaped function. Spatial memory function should be optimal at intermediate levels of CORT while performance is diminished when plasma CORT is high or low. The time course of effects suggest that adrenal steroids mediate spatial memory by genomic mechanisms. Further, rats that were first trained to the RAM before adrenal removal performed as well as controls suggesting that ADX impairs learning while leaving memory intact. The contribution of adrenal steroids to learning and/or memory appears complicated, however, since when these same rats were tested on a delay task, performance was improved in ADX rots.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
-
Program
-
Biopsychology
