Voltage-sensitive sodium channels appear to be an electrophysiological hallmark of gliomas. However, the expression of channel subtypes is unclear in these tumors. In this study different gliomas were investigated for the expression of sodium channel subtypes Na(v)1.1, Na(v)1.2, Na(v)1.3, Na(v)1.4, Na(v)1.6, and Na(x)(Na(v)2.1) using RT-PCR. At least one subtype of channels could be detected in each tumor. High-grade gliomas expressed fewer sodium channel subtypes and these at weaker levels than low-grade tumors. Expression of Na(v)1.6, the most abundant isoform in the CNS, was almost absent in the gliomas except the pilocytic variant. Our study gives clear evidence for a differential expression of sodium channel subtypes in gliomas and indicates a predominant expression of channels related to malignancy grades.

The whole-cell patch clamp technique was used to characterize voltage- and neurotransmitter-activated currents in the medulloblastoma cell line MHH-MED-3 and cells from tissue slices and primary cultures of two medulloblastoma biopsies. These preparations revealed similar electrophysiological properties. All tested cells displayed 4-aminopyridine-sensitive delayed rectifying K+ currents, γ-aminobutyric acidA receptor-mediated Cl− currents and most of them inward rectifier K+ currents. Transient inward currents were mainly carried by low-voltage activated T-type Ca2+ channels in MHH-MED-3 cells, and tetrodotoxin-sensitive Na+ channels in cells from the primary culture. From these characteristics we conclude that medulloblastoma cells share physiological features with developing cerebellar granule cells at an immature stage.