EFFECTS OF EXTRACELLULAR CESIUM ON EVOKED FIELD POTENTIALS IN THE AGED RAT DENTATE GYRUS

F.P. Houston¹; Z. Yang¹; M. Krause²*;
B.L. McNaughton¹; C.A. Barnes¹

1. NSMA, Univ Arizona, Tucson, AZ, USA
2. Tensor Biosciences, Irvine, CA, USA

Age-related changes within the hippocampus are known to account for normal senescent learning and memory deficits. Specific changes in the hippocampal dentate gyrus that contribute to these cognitive deficits include a decrease in NMDA-mediated synaptic response as well as frank synaptic loss. Recent evidence also indicates that reduced potassium currents in aged hippocampal synapses may also contribute to the age impairment (Alshuaib et al., 2001). The understanding of potassium channel function and its alteration with age is crucial, since dendritic signaling, temporal summation, and neuronal excitability are influenced by potassium currents. In vitro extracellular recordings were gathered from the dentate gyrus of young (5 month) and aged (27 month) F-344 rat behaviorally characterized on the Morris Swim Task. Hippocampal recordings at the granule cell-hilar boarder were obtained under normal ACSF and 1mM CsCl conditions. Data acquired during input/output stimulation show no significant differences in the population spike component of the field potential between the two age groups. While this may indicate that there are no changes in absolute number of potassium channels between young and old rats, it does not rule out differences in the distribution of these channels across the neuron.

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