Simultaneous recording of receptor current and intraciliary Ca 2+ 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 Ca 2+ concentration from isolated salamander olfactory receptor cells loaded with the fluorescent Ca 2+ 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 Ca 2+ homeostasis within the olfactory cilia, and are consistent with the notion that the oscillations induced by prolonged odour exposure represent the coupled oscillation of Ca 2+ and cyclic nucleotide concentrations.