English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The purpose of these experiments is to test whether the differences between normal and tetrodotoxin-resistant Na+ channels reside in the selectivity filter. To do this, we have compared the selectivity of batrachotoxin-activated channels for alkali cations, organic cations, and nonelectrolytes in two neuroblastoma clonal cell lines: N18, which has normal tetrodotoxin (TTX) sensitivity, and C9, which is relatively TTX-resistant. We have also studied the effect of H+ on Na+ permeability and on the interaction between TTX and its receptor site in both cell lines. There is no qualitative difference between the two cell lines in any of these properties. In both cell lines the batrachotoxin-activated Na+ channels have a selectivity sequence of Tl+ greater than Na+ greater than K+, guanidinium greater than Rb+ greater than Cs+, methylamine. Also, in both cell lines H+ blocks Na+ channels with a pKa of 5.5 and inhibits the action of TTX with the same pKa. These observations indicate that the selectivity filters of the Na+ channels in C9 and N18 do not differ significantly despite the 100-fold difference in TTX-affinity. Our selectivity studies of batrachotoxin-activated Na+ channels for both cell lines suggest that these toxin-activated Na+ channels have a limiting pore size of 3.8 x 6.0 A, as compared to a pore size of 3.0 x 5.0 A for potential-activated Na+ channels.

Comparison of ionic selectivity of batrachotoxin-activated channels with different tetrodotoxin dissociation constants.