Noise analysis of ion channels in non-space-clamped cables: estimates of channel parameters in olfactory cilia.
Ion channels in the cilia of olfactory neurons are part of the transduction machinery of olfaction. Odorant stimuli have been shown to induce a biphasic current response, consisting of a cAMP-activated current and a Ca(2+)-activated Cl- current. We have developed a noise analysis method to study ion channels in leaky cables, such as the olfactory cilium, under non-space-clamp conditions. We performed steady-state noise analysis on ligand-induced currents in excised cilia, voltage-clamped at input and internally perfused with cAMP or Ca2+. The cAMP-activated channels analyzed by this method gave results similar to those of single-channel recordings (gamma = 8.3 pS). Single-channel currents have not yet been recorded for the Ca(2+)-activated Cl- channels. Using our noise analysis method, we estimate a unit conductance, gamma = 0.8 pS, for these channels. The density of channels was found to be approximately 70 channels/micron2 for both channel species.
Larsson
H P
HP
Department of Molecular and Cell Biology, University of California Berkeley 94720, USA.
Kleene
S J
SJ
Lecar
H
H
D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002923:Cilia / Q000502:physiology*; D000242:Cyclic AMP / Q000494:pharmacology*; D004848:Epithelium / Q000294:innervation; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008956:Models, Chemical; D009831:Olfactory Mucosa / Q000294:innervation*; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011894:Rana pipiens; D012044:Regression Analysis
D007473:Ion Channels; D000242:Cyclic AMP; D002118:Calcium