Age-Related Deficits in Spatial Memory and Hippocampal Spines in Virgin, Female Fischer 344 Rats

Victoria N Luine,Maya Frankfurt,Maureen E Wallace

doi:10.1155/2011/316386

Abstract

Effects of aging on memory and brain morphology were examined in aged, 21-month-old, and young, 4-month-old, Fischer 344 female rats. Spatial memory was assessed using the object placement task, and dendritic spine density was determined on pyramidal neurons in the hippocampus following Golgi impregnation. Consistent with previous studies, aged females showed poorer object placement performance than young subjects. Young subjects significantly discriminated the location of objects with a 1.5-hour intertrial delay while aged subjects did not. Spine density of basal dendrites on CA1 pyramidal cells was 16% lower in the aged subjects as compared to the young subjects. No differences in spine density were found between young and aged subjects in basal dendrites of CA1 or in either dendritic field of CA3 pyramidal neurons. Thus, decreased hippocampal CA1 dendritic spine density in aged rats may contribute to poorer spatial memory as compared to young rats. The possibility that the neuroplastic changes observed in this study may pertain only to female subjects having had a specific set of life experiences is discussed. Different factors, such as reproductive status, diet, and handling may contribute to neuroplasticity of the brain during aging; however, this view requires further examination.

Highlights

It is well established that aging in animals and humans is accompanied by a decline in the ability to acquire and remember information
One week after spatial memory testing, spine density was assessed in hippocampal pyramidal neurons using Golgi impregnation to determine whether possible age-related declines in spatial memory are associated with changes in spine density in CA1 and CA3 hippocampal pyramidal neurons
Subjects were tested on the object placement task with intertrial delays of 1 and 1.5 h between the sample (T1) and the recognition trials (T2; Figures 2(a) and 2(b))

Summary

Introduction

It is well established that aging in animals and humans is accompanied by a decline in the ability to acquire and remember information. Markham et al [13], examining only females, showed that 19–22-month-old retired breeder, Long Evans rats did not have altered CA1 spine density as compared to 3–5 month old females. This general lack of agreement in findings on neuroplastic changes in the hippocampus with aging has been ascribed to possible sex and strain differences, but few studies have examined females [12, 13], and not all strains have been systematically compared. One week after spatial memory testing, spine density was assessed in hippocampal pyramidal neurons using Golgi impregnation to determine whether possible age-related declines in spatial memory are associated with changes in spine density in CA1 and CA3 hippocampal pyramidal neurons

Experimental Procedures

Results

Discussion