The present study was undertaken to investigate whether neural activity of hippocampal slices can be preserved after replacing D-glucose with glycolytic intermediate metabolites such as lactate, pyruvate and citrate or with other sugars such as fructose, mannose, maltose, glucosamine, sucrose and galactose. As an index of neural activity, population spikes (PS) were recorded in the granule cell layers after electrical stimulation to the perforant path of guinea pig hippocampal slices. In addition, we determined the levels of ATP and creatine phosphate (CrP) in each slice after the replacement of D-glucose with these substrates, and correlated it with the neural activity. Substrates other than D-glucose could not maintain the PS for even 20 min although the slices perfused with medium containing lactate, pyruvate, galactose, fructose and maltose maintained similar levels of ATP and CrP as in slices incubated in the D-glucose-containing medium. These results indicate that D-glucose is essential for the preservation of synaptic activity in addition to its main role as the substrate for energy production to maintain the levels of high energy phosphates.