Loss of Functional Voltage-gated Sodium Channels in Persistent Mumps Virus-infected PC12 Cells

1 Department of Physiology and 2 Department of Medical Microbiology and Immunology, School of Medicine, University of Minnesota-Duluth, Duluth, Minnesota, 55812-2487, U.S.A. Rat pheochromocytoma (PC12) cells, persistently infected with mumps virus (MV), failed to generate full-sized stimulus-evoked action potentials (SEAPs) when examined by intracellular electrophysiological recording techniques. Application of tetrodotoxin (TTX) had little or no effect on MV-reduced SEAPs, indicating that the number of functional voltage-gated Na + channels was decreased or their operation was blocked by the virus. In contrast, MV-infected cells generated normal Ca 2+ spikes when bathed in a solution containing TTX, tetraethylammonium ions and a high concentration (20 m M ) of Ca 2+ . In addition, when infected cells bathed in TTX were superfused with Co 2+ the SEAP profile reverted to that typical of PC12 cells with functional voltagegated K + channels only. These observations indicate that MV affects voltage-gated Na + channels, but spares voltage-gated Ca 2+ and K + channels of persistently infected cells. Keywords: mumps virus, persistent infection, ion channels Received 6 September 1988; accepted 15 November 1988.