Hp. Larsson et al., NOISE-ANALYSIS OF ION CHANNELS IN NON-SPACE-CLAMPED CABLES - ESTIMATES OF CHANNEL PARAMETERS IN OLFACTORY CILIA, Biophysical journal, 72(3), 1997, pp. 1193-1203
Ion channels in the cilia of olfactory neurons are part of the transdu
ction machinery of olfaction. Odorant stimuli have been shown to induc
e a biphasic current response, consisting of a cAMP-activated current
and a Ca2+-activated Cl- current. We have developed a noise analysis m
ethod to study ion channels in leaky cables, such as the olfactory cil
ium, 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-activate
d channels analyzed by this method gave results similar to those of si
ngle-channel recordings (gamma = 8.3 pS). Single-channel currents have
not yet been recorded for the Ca2+-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 similar t
o 70 channels/mu m(2) for both channel species.