Simultaneous recording of receptor current and intraciliary Ca2+ concentration in salamander olfactory receptor cells

1. The suction pipette technique was combined with laser spot fluorescence microscopy to record simultaneously odour-induced current responses and intraciliary Ca2+ concentration from isolated salamander olfactory receptor cells loaded with the fluorescent Ca2+ indicator fluo-3. 2. When exposed for 1 s to increasing odour concentrations both the suction pipette current and fluo-3 fluorescence increased dynamically, rising with a similar time course. Thereafter, the fluorescence signal decayed more slowly, outlasting the current response by 0.56 +/- 0.12 s. 3. The fluo-3 fluorescence evoked by progressively increasing odour concentrations varied in an approximately linear manner with the magnitude of the suction pipette current. 4. Prolonged odour stimulation evoked synchronous oscillations in both suction pipette current and intraciliary calcium concentration with a mean period of 4.5 +/- 0.3 s. 5. When external Na+ was omitted from the stimulating solution the oscillation period for both the current and fluorescence signals was lengthened by a factor of 1.9 +/- 0.2 in comparison with the oscillation period when stimulated in Ringer solution. 6. These results support the currently accepted mechanism for Ca2+ homeostasis within the olfactory cilia, and are consistent with the notion that the oscillations induced by prolonged odour exposure represent the coupled oscillation of Ca2+ and cyclic nucleotide concentrations.