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Functional interactions between the SK2 channel and the nicotinic acetylcholine receptor in enteric neurons of the guinea pig ileum
Author(s) -
Nakajima Hidemitsu,
Goto Hiroto,
Azuma YasuTaka,
Fujita Akikazu,
Takeuchi Tadayoshi
Publication year - 2007
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2007.04960.x
Subject(s) - choline acetyltransferase , enteric nervous system , apamin , acetylcholine , nicotinic agonist , cholinergic , myenteric plexus , biology , acetylcholine receptor , neurotransmitter , medicine , microbiology and biotechnology , endocrinology , receptor , chemistry , biophysics , biochemistry , potassium channel , immunology , immunohistochemistry
The neurotransmitter acetylcholine (ACh) plays a critical role in gastrointestinal function. The role of the small conductance Ca 2+ ‐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.