IP3-Gated Channels and their Occurrence Relative to CNG Channels in the Soma and Dendritic Knob of Rat Olfactory Receptor Neurons

IP3-Gated Channels and their Occurrence Relative to CNG Channels in the Soma and Dendritic Knob... Olfactory receptor neurons respond to odorants with G protein-mediated increases in the concentrations of cyclic adenosine 3′,5′-monophosphate (cAMP) and/or inositol-1,4,5-trisphosphate (IP3). This study provides evidence that both second messengers can directly activate distinct ion channels in excised inside-out patches from the dendritic knob and soma membrane of rat olfactory receptor neurons (ORNs). The IP3-gated channels in the dendritic knob and soma membranes could be classified into two types, with conductances of 40 ± 7 pS (n= 5) and 14 ± 3 pS (n= 4), with the former having longer open dwell times. Estimated values of the densities of both channels from the same inside-out membrane patches were very much smaller for IP3-gated than for CNG channels. For example, in the dendritic knob membrane there were about 1000 CNG channels ·μm−2 compared to about 85 IP3-gated channels ·μm−2. Furthermore, only about 36% of the dendritic knob patches responded to IP3, whereas 83% of the same patches responded to cAMP. In the soma, both channel densities were lower, with the CNG channel density again being larger (∼57 channels ·μm−2) than that of the IP3-gated channels (∼13 channels ·μm−2), with again a much smaller fraction of patches responding to IP3 than to cAMP. These results were consistent with other evidence suggesting that the cAMP-pathway dominates the IP3 pathway in mammalian olfactory transduction. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

IP3-Gated Channels and their Occurrence Relative to CNG Channels in the Soma and Dendritic Knob of Rat Olfactory Receptor Neurons

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2001 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-001-0013-5
Publisher site
See Article on Publisher Site

Abstract

Olfactory receptor neurons respond to odorants with G protein-mediated increases in the concentrations of cyclic adenosine 3′,5′-monophosphate (cAMP) and/or inositol-1,4,5-trisphosphate (IP3). This study provides evidence that both second messengers can directly activate distinct ion channels in excised inside-out patches from the dendritic knob and soma membrane of rat olfactory receptor neurons (ORNs). The IP3-gated channels in the dendritic knob and soma membranes could be classified into two types, with conductances of 40 ± 7 pS (n= 5) and 14 ± 3 pS (n= 4), with the former having longer open dwell times. Estimated values of the densities of both channels from the same inside-out membrane patches were very much smaller for IP3-gated than for CNG channels. For example, in the dendritic knob membrane there were about 1000 CNG channels ·μm−2 compared to about 85 IP3-gated channels ·μm−2. Furthermore, only about 36% of the dendritic knob patches responded to IP3, whereas 83% of the same patches responded to cAMP. In the soma, both channel densities were lower, with the CNG channel density again being larger (∼57 channels ·μm−2) than that of the IP3-gated channels (∼13 channels ·μm−2), with again a much smaller fraction of patches responding to IP3 than to cAMP. These results were consistent with other evidence suggesting that the cAMP-pathway dominates the IP3 pathway in mammalian olfactory transduction.

Journal

The Journal of Membrane BiologySpringer Journals

Published: May 15, 2001

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