Functional interactions between the SK2 channel and the nicotinic acetylcholine receptor in enteric neurons of the guinea pig ileum.
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 alpha3/5 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 alpha3/5 subunits of nAChR. These results suggest that SK2 channels negatively regulate the excitation of enteric neurons via functional interactions with nAChRs.
Nakajima
Hidemitsu
H
Laboratory of Veterinary Pharmacology, Graduate School of Life and Environmental Science, Osaka Prefecture University, Naka-ku, Sakai, Japan.
Goto
Hiroto
H
Azuma
Yasu-Taka
YT
Fujita
Akikazu
A
Takeuchi
Tadayoshi
T
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D017615:Enteric Nervous System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D006801:Humans; D007082:Ileum / Q000294:innervation* / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D021122:Protein Subunits / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D026902:Potassium Channel Blockers; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D051640:Small-Conductance Calcium-Activated Potassium Channels; C496898:Kcnn2 protein, mouse; C496900:Kcnn3 protein, mouse; C523972:CHRNA5 protein, mouse