Cilium-attached and excised patch-clamp recordings of odourant-activated Ca-dependent K channels from chemosensory cilia of olfactory receptor neurons.
It has previously been proposed that a Ca2+-dependent K+ conductance is implicated in the inhibitory odourant response in rat and toad olfactory receptor neurons. Previous whole-cell and single-channel measurements on inside-out excised patches, in addition to immunochemical evidence, indicated the presence of Ca2+-dependent K+ channels in olfactory cilia, the transducing structures of these sensory cells. Ca2+-dependent K+ channels opened in 'on-cilium' membrane patches from C. caudiverbera upon odourant stimulation. Furthermore, after excision in the inside-out configuration, the channel could be opened by micromolar Ca2+, in a Ca2+-dependent fashion, but it was unresponsive to cyclic AMP. We estimated that the Ca2+ concentration in the proximity of a Ca2+-dependent K+ channel within the cilia reaches at least 100 microM during the odour response. The K+ channel displayed a higher selectivity for K+ than for Na+. Our results support a role for this Ca2+-dependent K+ channel in chemotransduction.
Delgado
Ricardo
R
Millennium Institute for Advanced Studies in Cell Biology and Biotechnology, University of Chile, PO Box 653, Santiago, Chile.
Bacigalupo
Juan
J
D000818:Animals; D001001:Anura; D002118:Calcium / Q000494:pharmacology; D002628:Chemoreceptor Cells / Q000502:physiology*; D002923:Cilia / Q000502:physiology*; D000242:Cyclic AMP / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000166:cytology*; D018408:Patch-Clamp Techniques / Q000379:methods; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D013997:Time Factors
D024681:Potassium Channels, Calcium-Activated; D000242:Cyclic AMP; D002118:Calcium