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

The suction pipette technique was combined with laser spot fluorescence mic roscopy to record simultaneously odour-induced current responses and intrac iliary Ca2+ concentration from isolated salamander olfactory receptor cells loaded with the fluorescent Ca2+ indicator fluo-3. When exposed for 1 s to increasing odour concentrations both the suction pi pette current and fluo-3 fluorescence increased dynamically, rising with a similar time course. Thereafter, the fluorescence signal decayed more slowl y, outlasting the current response by 0.56 +/- 0.12 s. The fluo-3 fluorescence evoked by progressively increasing odour concentrat ions varied in an approximately linear manner with the magnitude of the suc tion pipette current. 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. When external Na+ was omitted from the stimulating solution the oscillation period for both the current and fluorescence signals was lengthened by a f actor of 1.9 +/- 0.2 in comparison with the oscillation period when stimula ted in Ringer solution. These results support the currently accepted mechanism for Ca2+ homeostasis within the olfactory cilia, and are consistent with the notion that the os cillations induced by prolonged odour exposure represent the coupled oscill ation of Ca2+ and cyclic nucleotide concentrations.