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 of a high (100 mM) K solution. High K+ induced an immediate current flux from cell to pipette, which was modeled as a depolarization of -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 (4-10s) 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 ~115 pS and depolarization of ~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., Lynch, J. W., & Barry, P. H. (1997). Odorant-induced currents in intact patches from rat olfactory receptor neurons: Theory and experiment. Biophysical Journal, 72(3), 1442–1457. https://doi.org/10.1016/S0006-3495(97)78791-5