Previously, we reported on the distinct effects of bioactive lysophospholipids, including lysophosphatidic acid (LPA), lysophosphatidylcholine (LPC), and sphingosylphosphorylcholine (SPC), on membrane potentials in rat C6 glioma cells. In the present report we have tested lysophosphatidylserine (LPS), another bioactive lysophospholipid, on membrane potentials in the same cell line. Membrane potentials were estimated by measuring the fluorescence changes of DiBAC-loaded glioma cells. LPS largely increased membrane potentials in a concentration-dependent manner. The LPS-induced membrane potential increases were not affected by treatment with pertussis toxin, implying no involvement of Gi/o proteins. In contrast to other lysophospholipids, the LPS-induced membrane potential increase was not diminished by a Na(+)-free media but was enhanced by suramin. Furthermore, this change was blunted by EIPA, an inhibitor of Na(+)/H(+) exchanger, but not by SITS, a specific inhibitor of bicarbonate transporter. Our observations suggest that LPS acts on membrane potentials in a unique manner in the C6 glioma cells, although the precise action mechanism requires additional investigation.