Abstract
1. The voltage clamp technique was used to study the effects of dendrotoxin (DTX) on outward potassium currents in internally perfused dorsal root ganglion neurones of guinea-pig. Sodium currents were eliminated by tetrodotoxin (TTX, 2 μmol/l), calcium currents and calcium-activated potassium conductances were abolished by intracellular perfusion of cells with KF. 2. Depolarizing voltage shifts from a holding potential of −90 mV yielded a fast transient outward current (I fK ) and a delayed non-inactivating outward current (I K/s). These currents could be separated by shifting the membrane potential to −50 mV, whereI fK was almost completely inactivated. 3. DTX, at concentrations of 0.14–1.4 nmol/l selectively reduced a portion of the non-inactivating potassium current, leaving the transient outward current unaffected. Once manifested, the action of DTX could not be reversed by washing. 4. The I–V characteristic of the current blocked by DTX is almost linear and quite different from the one of the ‘DTX-resistant’ portion ofI sK , which shows a non-linear I–V curve. 5. Tetraethylammonium (TEA, 30 mmol/l) strongly reducedI fK andI sK . However, subsequent application of DTX was still able to further reduceI sK . 6. 3,4-diaminopyridine (3,4-DAP, 500 μmol/l) unselectively reducedI fK and a portion ofI sK . The remainder of the latter could not further be reduced by DTX, suggesting a similar action of the two blockers on non-inactivating potassium currents. 7. From the results presented, it is suggested that dendrotoxin selectively blocks a non-inactivating subtype of potassium channel.
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This is part of the thesis of R.P. to be presented to the Fachbereich Biologie, Justus-Liebig-Universität Gießen
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Penner, R., Petersen, M., Pierau, F.K. et al. Dendrotoxin: a selective blocker of a non-inactivating potassium current in guinea-pig dorsal root ganglion neurones. Pflugers Arch. 407, 365–369 (1986). https://doi.org/10.1007/BF00652619
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DOI: https://doi.org/10.1007/BF00652619