Much of our present knowledge of glial cell function stems from studies of
glioma cell lines, both rodent (C6, C6
polyploid, and TR33B) and human (1321N1, 138MG, D384,
R-111, T67, Tp-276MG, Tp-301MG, Tp-483MG, Tp-387MG, U-118MG, U-251MG, U-373MG, U-787MG, U-1242MG, and UC-11MG). New methods such as patch clamp and Ca2+ imaging have lead to rapid progress the last few years in our knowledge about glial cells, where an unexpected presence and diversity of receptors and
ion channels have emerged. Basic mechanisms related to membrane potential and K+ transport and the presence of voltage gated
ion channels (Na+, inwardly rectifying K+, Ca(2+)-activated K+, Ca2+, and Cl- channels) have been identified. Receptor function and intracellular signaling for
glutamate,
acetylcholine,
histamine,
serotonin, cathecolamines, and a large number of
neuropeptides (
bradykinin,
cholecystokinin,
endothelin,
opioids, and
tachykinins) have been characterized. Such studies are facilitated in cell lines which offer a more homogenous material than primary cultures. Although the expression of
ion channels and receptors vary considerably between different cell lines and comparative studies are rare, a few differences (compared to astrocytes in primary culture) have been identified which may turn out to be characteristic for
glioma cells. Future identification of specific markers for receptors on glial and
glioma cells related to cell type and growth properties may have great potential in clinical diagnosis and
therapy.