Temporal development of cyclic nucleotide-gated and Ca2+ -activated Cl- currents in isolated mouse olfactory sensory neurons.
A Ca(2+)-activated Cl(-) current constitutes a large part of the transduction current in olfactory sensory neurons. The binding of odorants to olfactory receptors in the cilia produces an increase in cAMP concentration; Ca(2+) enters into the cilia through CNG channels and activates a Cl(-) current. In intact mouse olfactory sensory neurons little is known about the kinetics of the Ca(2+)-activated Cl(-) current. Here, we directly activated CNG channels by flash photolysis of caged cAMP or 8-Br-cAMP and measured the current response with the whole cell voltage-clamp technique in mouse neurons. We measured multiphasic currents in the rising phase of the response at -50 mV. The current rising phase became monophasic in the absence of extracellular Ca(2+), at +50 mV, or when most of the intracellular Cl(-) was replaced by gluconate to shift the equilibrium potential for Cl(-) to -50 mV. These results show that the second phase of the current in mouse intact neurons is attributed to a Cl(-) current activated by Ca(2+), similarly to previous results on isolated frog cilia. The percentage of the total saturating current carried by Cl(-) was estimated in two ways: 1) by measuring the maximum secondary current and 2) by blocking the Cl(-) channel with niflumic acid. We estimated that in the presence of 1 mM extracellular Ca(2+) and in symmetrical Cl(-) concentrations the Cl(-) component can constitute up to 90% of the total current response. These data show how to unravel the CNG and Ca(2+)-activated Cl(-) component of the current rising phase.
Boccaccio
Anna
A
International School for Advanced Studies, SISSA, Sector of Neurobiology, Basovizza, Trieste, Italy. aboccac@sissa.it
Menini
Anna
A
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D005942:Gluconates / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008807:Mice, Inbred BALB C; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009544:Niflumic Acid / Q000494:pharmacology; D009712:Nucleotides, Cyclic / Q000378:metabolism* / Q000494:pharmacology; D009831:Olfactory Mucosa / Q000166:cytology*; D018408:Patch-Clamp Techniques / Q000379:methods
C089981:(2-nitrophenyl)ethyl-cyclic adenosine monophosphate; D018118:Chloride Channels; D005942:Gluconates; D009712:Nucleotides, Cyclic; D015124:8-Bromo Cyclic Adenosine Monophosphate; D009544:Niflumic Acid; D000242:Cyclic AMP; C030691:gluconic acid; D002118:Calcium