title: Intensity of odorant stimulation affects mode of Ca2+ dynamics in rat olfactory receptor neurons.
abstract: We investigated the relation between the intensity of odorant stimulation and the mode of spatiotemporal Ca(2+) dynamics in Fluo-4-loaded rat olfactory receptor neurons (ORNs) using a confocal laser scanning microscope. We found that relatively smaller Ca(2+) transients remained confined to the knob while larger ones spread to the soma with latency. Prolonged odor exposure ensured the spread of Ca(2+) transients from the knob to the soma. Upon exposing ORNs to progressively increasing concentrations of odor, the Ca(2+) transients that were confined to the knob at lower concentrations extended to the soma at higher concentrations. Stimulation with progressively increasing concentrations of forskolin plus IBMX yielded identical results. Partial inhibition of adenylyl cyclase by MDL12330A changed the odor response extending to the soma to a response confined to the knob. Blocking of L-type Ca(2+) channels by nifedipine reduced the magnitude of the response extending to the soma but had no effect on the response confined to the knob. It is thus suggested that Ca(2+) transients confined to the knob represent weak stimulation, and, speculatively, such responses either constitute inhibitory responses or indicate weak excitatory responses that fail to outstand the spontaneous electrical noise of ORNs.
authors.affiliation: Laboratory of Physiology, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
authors.forename: Shree Hari
authors.initials: SH
authors.lastname: Gautam
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Otsuguro
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ito
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Saito
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Habara
mesh_terms: D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002923:Cilia / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D018035:Receptors, Odorant / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D012903:Smell / Q000187:drug effects / Q000502:physiology*; D014966:Xanthenes
chemical_list: D000814:Aniline Compounds; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; C409648:Fluo 4; D018035:Receptors, Odorant; D014966:Xanthenes; D002118:Calcium