title: Photolysis of caged cyclic AMP in the ciliary cytoplasm of the newt olfactory receptor cell.
abstract: The effects of cyclic nucleotide monophosphate (cNMP) in the ciliary cytoplasm of the olfactory receptor cell were examined by using photolysis of caged cNMP loaded from the whole-cell patch clamp pipette. Illumination of the cilia induced an inward current at -50 mV. The current amplitude was voltage dependent and the polarity was reversed at +10 mV. The amplitude of the light-induced current was dependent on both light intensity and duration. The intensity-response relation was fitted well by the Hill equation with a coefficient (n(H)) of 4.99 +/- 2.66 (mean +/- S.D., n = 19) and the duration-response relation with a coefficient of 4.03 +/- 1.43 (n = 17). The activation time course of adenylyl cyclase was estimated by comparing the light-induced response with the odorant-induced response. Adenylyl cyclase was activated approximately 260 ms later from the onset of the odorant-stimulation. The light-induced current developed very sharply. This could be explained by the sequential openings of cAMP-gated and Ca2+-activated Cl- channels. At +100 mV, where Ca2+ influx is expected to be very small, the current rising phase became less steep. When the cells were stimulated by long steps of either odour or light, the odorant-induced current showed stronger decay than the light-induced response. This observation suggests that the molecular system regulating desensitization is situated upstream of cAMP production.
authors.affiliation: Department of Biophysical Engineering, Osaka University, Japan. hiroko@bpe.es.osaka-u.jp
authors.forename: Hiroko
authors.initials: H
authors.lastname: Takeuchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kurahashi
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002923:Cilia / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D004594:Electrophysiology; D005246:Feedback; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000502:physiology; D008027:Light; D008564:Membrane Potentials / Q000502:physiology; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010782:Photolysis; D012455:Salamandridae / Q000502:physiology*
chemical_list: D007473:Ion Channels; D000242:Cyclic AMP; D000262:Adenylyl Cyclases