Journal of Neurophysiology, Vol 73, Issue 2 562-567, Copyright © 1995 by APS

ARTICLES

Interaction of anionic and cationic currents leads to a voltage dependence in the odor response of olfactory receptor neurons

S. Firestein and G. M. Shepherd
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.

1. We recorded odor-induced currents from isolated olfactory receptor neurons of the land phase tiger salamander (Ambystoma tigrinum) with the whole cell patch clamp. 2. In a subset of cells the current-voltage relation for the odor-induced current showed a strong rectification with, in some cells, a negative resistance slope between about -45 and -25 mV. In these cells there was little or no odor-induced current at -55 mV, the average resting potential of olfactory neurons. 3. Depolarizing the membrane to +20 mV revealed a large outward current, and on repolarizing the membrane to -55 mV we could observe a large inward current. This current was not observed in the absence of the depolarizing step or in the absence of odor stimuli. 4. This odor-induced tail current was dependent on extracellular Ca2+ and voltage, activating with increased depolarization. The reversal potential was sensitive to the chloride equilibrium potential and it could be significantly blocked by niflumic acid, a blocker of calcium-activated chloride currents. The voltage dependence could result from either the voltage-dependent block of adenosine 3',5'-cyclic monophosphate-gated cation channels known to be activated by odorants and permeable to Ca2+, or from an inherent voltage dependence in the chloride channel gating. 5. The current appears to function as a regenerative mechanism that might increase the amplitude and duration of the odor-induced current, especially to low concentrations of stimulus.

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