Related Experiment Video
Updated: Aug 19, 2026

Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins
Published on: May 22, 2017
Unitary currents through K+ selective channelrhodopsins reveal multiple conductance states within an activated state
Klaus Benndorf1, Ralf Schmauder1, Peter Hegemann2
1Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena 07740, Germany.
None:
The analysis of how sensation, cognition, and behavior arise from neuronal activity has been enormously facilitated by optogenetics, using algae-derived light sensitive channelrhodopsins, ChRs, expressed in brain cells. To disclose the unitary conductance and the details of the gating mechanism, we recorded unitary currents of the potentially inhibitory K+ selective ChRs HcKCR1 and WiChR1 at femtosiemens resolution. Both ChRs open in bursts with a large dominating conductance of 1.6 pS for KCR1 and 2.4 pS for WiChR1 but they are accompanied by widely distributed conductance levels covering a continuum of between 0.3 and 3.0 pS. In WiChR1, these bursts are approximately four times longer than in KCR1. The photocycle and the closed-open gating in an activated state complex seem to be two orthogonal processes. The single-channel currents of the two ChRs explain all characteristic features of the respective whole-cell currents. Our data provide insight into exceptionally small and heterogeneous conductance levels of single channelrhodopsin molecules and open the door to tailor specific tools for optogenetic control in neurons of brain networks.
Related Concept Videos
Channel Rhodopsins
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
Ligand-Gated Ion Channel Receptor: Gating Mechanism
G-Protein Gated Ion Channels
Sensory organs,...
Ligand-gated Ion Channels
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that include the...
Ligand-gated Ion Channels
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that include the...
Mechanically-gated Ion Channels

