The measurements of unitary outward ion currents in unidentified neurons of the snailHelix pomatia with the patch-clamp technique in a cell-attached configuration showed the presence of several types of K+ channels. We investigated three types of K+ channels: with big (75 pS, BKC), medium (22 pS, MKC), and small (6.2 pS, SKC) unitary conductance. BKC and MKC were activated at a membrane potential of about −30 mV, whereas SKC were activated at more negative potentials, with opening probability of the latter channels significantly decreasing at potentials more positive than −30 mV. Pharmacological investigation showed that BKC and MKC channel activity disappeared after 8–10 min of cell patching with a pipette solution containing 60 mM Cs+, whereas MKC channels remained unaffected. BKC and MKC were proved to be more sensitive to TEA (20 mM), whereas SKC were selectively sensitive to 4-AP (10 mM). Cd2+ (100 µM) in the pipette solution decreased the unitary conductance of BKC channels by 55 % and that of MKC channels by about 31 %. In contrast, the unitary conductance of SKC channels was not changed by the above blocker. Bath application of 10 µM 5-HT showed that MKC were suppressed by 5-HT, whereas SKC and BKC were insensitive to this transmitter. It is supposed that BKC can be classified as big-conductance Ca2+-dependent K+ channels (KCa) or to 5-HT-sensitive K+ channels (S-type channels), while MKC correspond to intermediate-conductance KCa, and SKC channels comply well with the characteristics of A-type K+ current.
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Neirofiziologiya/Neurophysiology, Vol. 28, No. 6, pp. 250–259, November–December, 1996.
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Lukyanetz, E.A., Sotkis, A.V. Characterization of single K+ channels inHelix pomatia neurons. Neurophysiology 28, 193–201 (1996). https://doi.org/10.1007/BF02252851
- Membrane Potential
- Channel Activity
- Negative Potential
- Pipette Solution
- Bath Application