Inward rectification in rat olfactory receptor neurons

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Abstract
Inwardly rectifying currents in enzymically dissociated olfactory receptor neurons of rat were studied by using patch-clamp techniques. Upon hyperpolarization to membrane potentials more negative than -100 mV, small inward-current relaxations were observed. Activation was described by a single exponential with a time constant that decreased e-fold for a 21 mV hyperpolarization. The current was not reduced by the external application of 5 mM Ba$^{2+}$, but was abolished by the addition of 5 mM Cs$^{+}$ to the bath solution. Increasing the external K$^{+}$ concentration ([K$^{+}$]$_{\text{o}}$) to 25 mM dramatically enhanced the current without affecting the voltage range or the kinetics of activation. In 25 mM [K$^{+}$]$_{\text{o}}$, tail currents reversed at -26 mV, significantly more positive than the K$^{+}$ equilibrium potential of -44 mV. These characteristics are consistent with those of a mixed Na$^{+}$/K$^{+}$ inward rectification that has been reported in several types of neuronal, cardiac and smooth muscle cells. The current may contribute to controlling cell excitability during the response to some odorants.