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Decreased glutamate release correlates with elevated dynorphin content in the hippocampus of aged rats with spatial learning deficits

Decreased glutamate release correlates with elevated dynorphin content in the hippocampus of aged... The effects of aging on extracellular glutamate and tissue dynorphin content in the hippocampus were examined in Fischer‐344 rats. Young adult (4‐month‐old) and aged (24‐month‐old) rats were trained to find a hidden platform in the Morris water task. Aged rats were unable to acquire the spatial learning task as rapidly as young controls. Following behavioral testing, an in vivo microdialysis perfusion method was used to determine extracellular glutamate levels in the hippocampus. There was a 25–35% reduction in extracellular glutamate concentration in both dorsal and ventral hippocampus of aged rats compared to young rats, in the absence of any change in tissue glutamate levels. Radioimmunoassay showed an increase in dynorphin A(1–8)‐like immunoreactivity [DYN‐A(1–8)LI] in both dorsal and ventral hippocampus, but not striatum, of aged rats. Immunocytochemistry indicated that this increase was localized to the dentate granule cells and mossy fibers. Furthermore, among the aged rats the increase in DYN‐A(1–8)LI was inversely correlated with the decrease in extracellular glutamate. These results suggest that the disregulation of dynorphin observed in cognitively impaired aged rats is related to reduced excitatory transmission within the hippocampal formation. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Hippocampus Wiley

Decreased glutamate release correlates with elevated dynorphin content in the hippocampus of aged rats with spatial learning deficits

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References (30)

Publisher
Wiley
Copyright
Copyright © 1991 Wiley Subscription Services
ISSN
1050-9631
eISSN
1098-1063
DOI
10.1002/hipo.450010407
pmid
1688281
Publisher site
See Article on Publisher Site

Abstract

The effects of aging on extracellular glutamate and tissue dynorphin content in the hippocampus were examined in Fischer‐344 rats. Young adult (4‐month‐old) and aged (24‐month‐old) rats were trained to find a hidden platform in the Morris water task. Aged rats were unable to acquire the spatial learning task as rapidly as young controls. Following behavioral testing, an in vivo microdialysis perfusion method was used to determine extracellular glutamate levels in the hippocampus. There was a 25–35% reduction in extracellular glutamate concentration in both dorsal and ventral hippocampus of aged rats compared to young rats, in the absence of any change in tissue glutamate levels. Radioimmunoassay showed an increase in dynorphin A(1–8)‐like immunoreactivity [DYN‐A(1–8)LI] in both dorsal and ventral hippocampus, but not striatum, of aged rats. Immunocytochemistry indicated that this increase was localized to the dentate granule cells and mossy fibers. Furthermore, among the aged rats the increase in DYN‐A(1–8)LI was inversely correlated with the decrease in extracellular glutamate. These results suggest that the disregulation of dynorphin observed in cognitively impaired aged rats is related to reduced excitatory transmission within the hippocampal formation.

Journal

HippocampusWiley

Published: Jan 1, 1991

Keywords: ; ;

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