Hyperglycemia-related neuronal excitability and epileptic seizures are not uncommon in clinical practice. However, their underlying mechanism remains elusive. ATP-sensitive K+ (KATP) channels are found in many excitable cells, including cardiac myocytes, pancreatic β cells, and neurons. These channels provide a link between the electrical activity of cell membranes and cellular metabolism. We investigated the effects of higher extracellular glucose on hippocampal KATP channel activities and neuronal excitability. The cell-attached patch-clamp configuration on cultured hippocampal cells and a novel multielectrode recording system on hippocampal slices were employed. In addition, a simulation modeling hippocampal CA3 pyramidal neurons (Pinsky-Rinzel model) was analyzed to investigate the role of KATP channels in the firing of simulated action potentials. We found that incremental extracellular glucose could attenuate the activities of hippocampal KATP channels. The effect was concentration dependent and involved mainly in open probabilities, not single-channel conductance. Additionally, higher levels of extracellular glucose could enhance neuropropagation; this could be attenuated by diazoxide, a KATP channel agonist. In simulations, high levels of intracellular ATP, used to mimic increased extracellular glucose or reduced conductance of KATP channels, enhanced the firing of action potentials in model neurons. The stochastic increases in intracellular ATP levels also demonstrated an irregular and clustered neuronal firing pattern. This phenomenon of KATP channel attenuation could be one of the underlying mechanisms of glucose-related neuronal hyperexcitability and propagation. © 2007 Wiley-Liss, Inc.