Characterization of K(+) currents using an in situ patch clamp technique in body wall muscle cells from Caenorhabditis elegans.

The properties of K(+) channels in body wall muscle cells acutely dissected from the nematode Caenorhabditis elegans were investigated at the macroscopic and unitary level using an in situ patch clamp technique. In the whole-cell configuration, depolarizations to potentials positive to -40 mV gave rise to outward currents resulting from the activation of two kinetically distinct voltage-dependent K(+) currents: a fast activating and inactivating 4-aminopyridine-sensitive component and a slowly activating and maintained tetraethylammonium-sensitive component. In cell-attached patches, voltage-dependent K(+) channels, with unitary conductances of 34 and 80 pS in the presence of 5 and 140 mM external K(+), respectively, activated at membrane potentials positive to -40 mV. Excision revealed that these channels corresponded to Ca(2+)-activated K(+) channels exhibiting an unusual sensitivity to internal Cl(-) and whose activity progressively decreased in inside-out conditions. After complete run-down of these channels, one third of inside-out patches displayed activity of another Ca(2+)-activated K(+) channel of smaller unitary conductance (6 pS at 0 mV in the presence of 5 mM external K(+)). In providing a detailed description of native K(+) currents in body wall muscle cells of C. elegans, this work lays the basis for further comparisons with mutants to assess the function of K(+) channels in this model organism that is highly amenable to molecular and classical genetics.