Odorant-induced currents in intact patches from rat olfactory receptor neurons: theory and experiment.
Odorant-induced currents in mammalian olfactory receptor neurons have proved difficult to obtain reliably using conventional whole-cell recording. By using a mathematical model of the electrical circuit of the patch and rest-of-cell, we demonstrate how cell-attached patch measurements can be used to quantitatively analyze responses to odorants or a high (100 mM) K+ solution. High K+ induced an immediate current flux from cell to pipette, which was modeled as a depolarization of approximately 52 mV, close to that expected from the Nernst equation (56 mV), and no change in the patch conductance. By contrast, a cocktail of cAMP-stimulating odorants induced a current flux from pipette into cell following a significant (4-10 s) delay. This was modeled as an average patch conductance increase of 36 pS and a depolarization of 13 mV. Odorant-induced single channels had a conductance of 16 pS. In cells bathed with no Mg2+ and 0.25 mM Ca2+, odorants induced a current flow from cell to pipette, which was modeled as a patch conductance increase of approximately 115 pS and depolarization of approximately 32 mV. All these results are consistent with cAMP-gated cation channels dominating the odorant response. This approach, which provides useful estimates of odorant-induced voltage and conductance changes, is applicable to similar measurements in any small cells.
Chiu
P
P
School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia.
Lynch
J W
JW
Barry
P H
PH
D000818:Animals; D000242:Cyclic AMP / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D008956:Models, Chemical; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D007473:Ion Channels; D000242:Cyclic AMP; D011188:Potassium