Abstract
Olfactory transduction starts at the sensory cilia that have 100 nm diameters. This signal transduction is now fairly well known to be conducted with cAMP metabolisms. Up to this point, however, knowledge about the spatial distribution of the system is very limited, mainly because of technical limitations accompanying the fine ciliary structure. To overcome these difficulties, we employed a combined technique of the patch clamp and photolysis of caged compound under fine visualization of sub-micron structure with the laser confocal microscope. Cilia were loaded with both caged cAMP for photolysis and Lucifer yellow for luminescent visualization. The laser light spot for photolysis was collected at the focal plane with the objective lens having a large NA(1.4) and with the short wavelength light (364 nm). When the intensity of the UV spot was assumed to express spatially a two-dimensional Gaussian distribution, σ was estimated to be < 300 nm. The On-Off and position of the UV spot were regulated by the AOTF device and Galvano-mirror. When local area (ca. 1 μm length) of cilium was illuminated (therefore, when local cAMP was jumped), the cell showed an inward current response of–10 pA at -50 mV. The current was observed at any part of cilia, but the amplitude gradually became smaller when the position was moved to the apical part. This may be consistent with the fact that the apical part becomes thinner than the proximal part. We conclude that olfactory transduction channels are present along entire cilium, presumably depending on the membrane area. [J Physiol Sci. 2007;57 Suppl:S18]
