Influence of age on the clearance of K+ from the extracellular space of rat hippocampal slices.
We examined the hypotheses that aging alters the capacity of brain tissue to regulate extracellular K+ activity (K+o), and that age-related decreases in glucose metabolism may underlie these alterations. Hippocampal slices from young adult (6-9 months old), middle-aged (16-19 months old), and aged (26-29 months old) Fischer 344 rats were exposed to physiological solutions containing 5-20 mM glucose maintained at 36-37 degrees C. Schaffer collaterals in each slice were stimulated at 40 Hz for 2 s, and the resulting changes in K+o were recorded with K+o-sensitive microelectrodes placed in stratum pyramidale of hippocampal subfield CA1. We found that K+ clearance from the extracellular space of hippocampal slices was significantly slowed in the middle-aged group compared with the young adult group in physiological solutions containing 5 and 10 mM glucose. Age-related differences in K+o clearance disappeared in 20 mM glucose. Also, the rate of K+o clearance was modified by glucose concentration. These results suggest that K+ transport rates are modified by age, and that age-related alterations in glucose metabolism may be involved.
Roberts
E L
EL
Department of Neurology, University of Miami School of Medicine, FL 33136, USA.
Feng
Z C
ZC
D000375:Aging / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D004558:Electric Stimulation; D005110:Extracellular Space / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D006624:Hippocampus / Q000254:growth & development / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D012044:Regression Analysis; D013997:Time Factors
D005947:Glucose; D011188:Potassium