Functional interactions between the SK2 channel and the nicotinic acetylcholine receptor in enteric neurons of the guinea pig ileum
Article first published online: 15 SEP 2007
© 2007 The Authors. Journal Compilation © 2007 International Society for Neurochemistry
Journal of Neurochemistry
Volume 103, Issue 6, pages 2428–2438, December 2007
How to Cite
Nakajima, H., Goto, H., Azuma, Y.-T., Fujita, A. and Takeuchi, T. (2007), Functional interactions between the SK2 channel and the nicotinic acetylcholine receptor in enteric neurons of the guinea pig ileum. Journal of Neurochemistry, 103: 2428–2438. doi: 10.1111/j.1471-4159.2007.04960.x
- Issue published online: 15 SEP 2007
- Article first published online: 15 SEP 2007
- Received February 7, 2007; revised manuscript received August 10, 2007; accepted August 13, 2007.
- acetylcholine release;
- guinea pig ileum;
- nicotinic acetylcholine receptor;
- SK2 subunit;
- small conductance Ca2+-activated K+ channels
The neurotransmitter acetylcholine (ACh) plays a critical role in gastrointestinal function. The role of the small conductance Ca2+-activated K+ (SK) channel in ACh release was examined using myenteric plexus preparations of guinea pig ileum. Apamin, an inhibitor of the SK channel, significantly enhanced nicotine-induced ACh release, but neither electrical field stimulation- nor 5-hydroxytryptamine-induced ACh release, suggesting that SK channels might be selectively involved in the regulation of nicotine-induced ACh release. Therefore, we investigated the distribution of SK2 and SK3 subunits and the interaction between SK2 channels and nicotinic ACh receptors (nAChRs) in the guinea pig ileum. The immunoreactivity of SK2 subunits was located in enteric neuronal cells. Furthermore, SK2-immunoreactive cells stained with an antibody for choline acetyltransferase, a marker for cholinergic neurons, and with an antibody for the α3/5 subunits of nAChR. In contrast, immunoreactivity of SK3 subunits was not found in enteric neurons. A co-immunoprecipitation assay with Triton X-100-soluble membrane fractions prepared from the ileum revealed an association of the SK2 subunit with the α3/5 subunits of nAChR. These results suggest that SK2 channels negatively regulate the excitation of enteric neurons via functional interactions with nAChRs.