The PH Buffering Capacity of Hippocampal Slices from Young Adult and Aged Rats

We examined the hypothesis that aging alters the capacity of brain tissue to buffer intracellular pH changes. Intracellular buffering power was determined in hippocampal slices from young adult and aged rats by raising the partial pressure of CO2. Changes in intracellular and extracellular pH in response to increases and decreases in CO2 were measured simultaneously with spectrophotometry and pH-sensitive microelectrodes. The intrinsic buffering power did not differ between young adult (25.6 +/- 11.1 mM) and aged (28.2 +/- 8.6 mM) slices. However, the bicarbonate buffering power was higher in young adult slices (72.52 +/- 5.07 mM) compared with aged slices (58.67 +/- 5.78 mM) since the resting intracellular pH was about 0.1 unit lower in aged slices. This decreased bicarbonate buffering capacity may contribute to the increased vulnerability of the aged brain to metabolic stress.