Noninvasive measurement of chloride concentration in rat olfactory receptor cells with use of a fluorescent dye.
Inwardly directed Ca(2+)-dependent chloride currents are thought to prolong and boost the odorant-induced transient receptor currents in olfactory cilia. Cl(-) inward current, of course, requires a sufficiently high intracellular Cl(-) concentration ([Cl(-)](i)). In previous measurements using a fluorescent Cl(-) probe, N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE), [Cl(-)](i) of newt olfactory cells was estimated to be only 40 mM. This low value led us to reexamine the [Cl(-)](i) by an improved procedure. When isolated rat olfactory neurons were bathed in Tyrode's solution (150 mM Cl(-)) at room temperature, the [Cl(-)] was 81.5 +/- 13.5 mM (mean +/- SE) in the tip of the dendrite (olfactory knob) and 81.8 +/- 10.2 mM (mean +/- SE) in the soma. The corresponding Cl(-) equilibrium potentials were -15.4 and -15.3 mV, respectively. Therefore, at resting potentials in the range of -90 to -50 mV, Cl(-) currents are predicted to be inward and capable of contributing to the depolarization induced by odorants. Yet, if the cell was depolarized beyond -15 mV, somal Cl(-) currents would be outward and facilitate repolarization during excitation. The measured [Cl(-)] in soma and knob are of interest, because in the cilia the chloride content may be expected to equilibrate with that of the knob in the resting state. They provide a starting point for the decrease in ciliary [Cl(-)] predicted to occur during transduction.
Kaneko
H
H
Department of Applied Physics and Chemistry, Division of Bio-Informatics, The University of Electro-Communications, Chofu, Tokyo 182 - 8585, Japan.
Nakamura
T
T
Lindemann
B
B
D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000032:analysis* / Q000378:metabolism*; D002923:Cilia / Q000737:chemistry / Q000378:metabolism; D004594:Electrophysiology; D005456:Fluorescent Dyes; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism*; D011806:Quinolinium Compounds; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013268:Stimulation, Chemical
D018118:Chloride Channels; D002712:Chlorides; D005456:Fluorescent Dyes; D011806:Quinolinium Compounds; C085493:N-(ethoxycarbonylmethyl)-6-methoxyquinolinium