S. Firestein et Gm. Shepherd, INTERACTION OF ANIONIC AND CATIONIC CURRENTS LEADS TO A VOLTAGE-DEPENDENCE IN THE ODOR RESPONSE OF OLFACTORY RECEPTOR NEURONS, Journal of neurophysiology, 73(2), 1995, pp. 562-567
1. We recorded odor-induced currents from isolated olfactory receptor
neurons of the land phase tiger salamander (Ambystoma trigrinum) with
the whole cell patch clamp. 2. In a subset of cells the current-voltag
e 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. Depolar
izing the membrane to +20 mV revealed a large outward current, and on
repolarizing the membrane to -55 mV we could observe a large inward cu
rrent. This current was not observed in the absence of the depolarizin
g step or in the absence of odor stimuli. 4. This odor-induced tail cu
rrent 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. Th
e voltage dependence could result from either the voltage-dependent bl
ock of adenosine 3',5'-cyclic monophosphate-gated cation channels know
n to be activated by odorants and permeable to Ca2+, or from an inhere
nt voltage dependence in the chloride channel gating. 5. The current a
ppears to function as a regenerative mechanism that might increase the
amplitude and duration of the odor-induced current, especially to low
concentrations of stimulus.