Distribution, amplification, and summation of cyclic nucleotide sensitivities within single olfactory sensory cilia

Submicron local cAMP elevation was used to map the distribution of transduction channels in single olfactory cilia. After the fine fluorescent visualization of the cilium with the laser-scanning confocal microscope, the intraciliary cAMP was jumped locally with the laser beam that photolyzes cytoplasmic caged compounds. Simultaneously, cells' responses were obtained with the whole-cell patch clamp. Responses were observed anywhere within the cilia, showing the broad distribution of transduction channels. For odor detection, such distribution would be useful for expanding the available responding area to increase the quantum efficiency. Also, the stimulus onto only 1 microm region induced >100 pA response operated by >700-2300 channels, although only 1 pA is sufficient for olfactory cells to generate action potentials. The large local response indicates a presence of strong amplification achieved with a high-density distribution of the transduction channels for the local ciliary excitation.