InsP₃-gated ion channels in rat olfactory cilia membrane

InsP₃-gated channels present in isolated rat olfactory cilia membranes were studied by recording current fluctuations in cilia membranes fused onto phospholipid bilayers formed at the tip of a patch pipette. We found that InsP₃ (1.25 to 30 μM) induced current fluctuations in 18 of 157 otherwise silent bilayers. The ion channels opened by InsP₃ could be classified into two groups that differed in terms of conductance and kinetics. One channel, which had a conductance of 37 pS, displayed two current levels, and the larger single channel currents were associated with longer open dwell times. The other channel displayed a larger conductance (103-184 pS). Both types of channels displayed reversal potentials near zero millivolts, consistent with nonspecific cation channels. These experiments suggest that mammalian olfactory neurons posess two types of ciliary InsP₃ gated channels.