Comparison of a Ca(2+)-gated conductance and a second-messenger-gated conductance in rat olfactory neurons.
The effect of a rise in intracellular Ca(2+) concentration was analyzed in isolated rat olfactory neurons using a whole-cell patch-clamp technique. Intracellular dialysis of 1 mmol l(-)(1) Ca(2+) in a standard-K(+), low-Cl(-) internal solution (E(Cl)=-69 mV) from the patch pipette into the olfactory neurons induced a sustained outward current of 49+/-5 pA (N=13) at -50 mV in all the cells examined. The outward currents were inhibited by external application of 100 micromol l(-)(1) 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB). External application of a Ca(2+) ionophore, 3 micromol l(-)(1) ionomycin, induced an inward current in three of eight cells whose voltages were clamped using the gramicidin-perforated technique, but ionomycin elicited an outward current in the other five cells, suggesting that natural intracellular Cl(-) concentration in the olfactory neurons was heterogeneous. While intracellular dialysis of 50 micromol l(-)(1) inositol 1,4,5-trisphosphate (1,4,5-InsP(3)) in the standard-K(+), low-Cl(-) internal solution induced the NPPB-sensitive outward current in 31 % of cells, and 500 micromol l(-)(1) cAMP induced it in 21 % of cells, a large proportion of the cells displayed an inward current in response to 1,4,5-InsP(3) and cAMP. The results suggest that 1,4,5-InsP(3) and cAMP can elicit Ca(2+)-dependent Cl(-) conductance and Ca(2+)-independent cation conductance in rat olfactory neurons.
Okada
Y
Y
Department of Physiology, Nagasaki University School of Dentistry, Nagasaki 852-8588, Japan. okada@net.nagasaki-u.ac.jp
Fujiyama
R
R
Miyamoto
T
T
Sato
T
T
D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D015640:Ion Channel Gating; D009579:Nitrobenzoates / Q000494:pharmacology; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar
D015220:Calcium Channels; D018118:Chloride Channels; D009579:Nitrobenzoates; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP