Attenuation of evoked field potentials from dentate granule cells by low glucose, pyruvate + malate, and sodium fluoride.

Extracellular field potentials were evoked from granule cells of the dentate gyrus by stimulation of the perforant path of the hippocampal slice, superfused with medium containing 10 mM glucose. Decreasing the glucose concentration to 2 mM caused a large but reversible attenuation of the rate of rise of population excitatory postsynaptic potential (EPSP) and of the population spike amplitude. Similar behaviour was observed in the presence of 5 mM glucose, although the decrease in EPSP was much less marked. Substitution of pyruvate + malate (2 mM, 0.2 mM) for glucose in the superfusion medium strongly depressed both EPSP and population spike. Sodium fluoride (1 mM) attenuated the population spike without affecting the EPSP. It is suggested that the behaviour of the evoked granule cell responses in the presence of lowered glucose or alternative substrates does not correlate with the energy state of the tissue.