Amiloride-insensitive cation conductance in Xenopus laevis olfactory neurons: a combined patch clamp and calcium imaging analysis.

We used digital calcium imaging with Fura-2 in conjunction with the tight-seal whole-cell patch clamp technique to describe a novel cation conductance in olfactory neurons of the clawed toad Xenopus laevis. Substitution of extracellular Ca2+ and Na+ was used as a tool to change [Ca2+]i. When [Ca2+]i was increased to about 450 nM, a conductance gcat activated that was permeable for cations. Upon gcat activation, an increase in [Ca2+]i occurred in the dendritic knob. Once activated, gcat showed no further dependence upon [Ca2+]i. Icat is shown to be different from the current activated by a mixture of the odorants citralva and amyl acetate. We conclude that there are two different cation conductances in the peripheral compartments of olfactory neurons in X. laevis.