T. Leinderszufall et al., IMAGING ODOR-INDUCED CALCIUM TRANSIENTS IN SINGLE OLFACTORY CILIA - SPECIFICITY OF ACTIVATION AND ROLE IN TRANSDUCTION, The Journal of neuroscience, 18(15), 1998, pp. 5630-5639
The possibility that odor stimuli trigger distinct Ca2+ elevations wit
hin the cilia of vertebrate olfactory receptor neurons (ORNs) is a wid
ely proposed concept. However, because of the small size of the olfact
ory cilia, the existence and properties of such Ca2+ elevations and th
eir role in odor transduction are still unknown. We investigate odor-i
nduced Ca2+ changes in individual olfactory cilia from salamander usin
g the Ca2+ indicator dye fluo-3 in combination with laser scanning con
focal microscopy. Single brief applications of odor ligand produce hig
hly localized Ca2+ elevations in individual cilia lasting for several
seconds. These Ca2+ signals originate in the cilia and depend entirely
on Ca2+ entry through ciliary cyclic nucleotide-gated ion channels. T
he odor specificity of the Ca2+ rises implies a receptor-operated mech
anism underlying odor detection. Each of the cilia on a receptor neuro
n functions as an independent biochemical compartment that can detect
odorants and produce a Ca2+ transient with remarkably uniform properti
es in terms of kinetics and odor specificity. The rate of recovery of
the odor-induced Ca2+ transients matches recovery from a short-term fa
rm of odor adaptation. Application of the membrane-permeant intracellu
lar Ca2+ chelator BAPTA AM eliminates this odor adaptation. The result
s indicate that an olfactory cilium serves as a basic functional unit
at the input level of the olfactory system, controlling both the speci
ficity and sensitivity of odor detection.