Sodium Channel Sensitivity to Saxitoxin and Tetrodotoxin in Clonal and Primary Cell Cultures as in Vitro Model Systems.
Abstract
Cellular model systems for saxitoxin (STX) and tetrodotoxin (TTX) block of voltage dependent sodium channels would be useful in the study of toxin action. Consequently, a variety of cells in tissue culture have been examined for suitability as model systems. The effectiveness of STX or TTX in blocking sodium channels was assessed by measuring the dose-dependent reduction in peak sodium current in patch-clamped clonal or dissociated CNS cells. Potassium currents were suppressed by 140 mM Cs(+) in the patch pipette and 10 mM TEA(+) in the bathing solution. In the clonal AtT20/D16-16 and NG108-15 cell lines, sodium currents were depressed completely by TTX with high affinity (IC50's of 7.6 nM and 6.5 nM respectively). By contrast, cells from the HCN-lA human cortical cell line gave more complicated results. Application of TTX suppressed 56% of the sodium current with an IC50 of 21.6 nM while the remaining current required an IC50 of 5.3 um. STX gave similar results with 29% of the sodium current blocked with an IC50 of 1.6 nM and the remaining 71% blocked with an IC50 of 1.25 uM. Differentiation of the HCN-1A cells with nerve growth factor and dibutyryl-cAMP yielded cells with mature neuronal morphologies but with similar toxin sensitivities. Such mixes of high and low toxin sensitivity have been shown in peripheral ganglia, but this is the first instance in a cell of CNS origin.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 13, 1993
- Accession Number
- ADP008878
Entities
People
- R. E. Sheridan
- S. S. Deshpande
Organizations
- United States Army Medical Research Institute of Chemical Defense