Cholinergic regulation of ion transport in the large intestine

anglicky Acetylcholine is one of the most important mediators of enteric nervous system involved in the regulation of ion transport in the large intestine. Although, recently, plenty of new evidences of various expression of ion transport proteins in distal and proximal colon was published, there still lacks an electrophysiological study comparing these parts of colon considering all that new findings. The aim of this study was thus to compare cholinergic regulation of ion transport in distal and proximal colon. We measured responses of distal and proximal colon in Ussing chambers by voltage-clamp method. The colonic epithelium was clamped to 0 mV and responses were recorded as changes of short-circuit current (SCC). Instead of acetylcholine we used its stable analogue carbachol. Data were processed and analyzed using a VBA code I wrote for this purpose for MS Excel 2007. We confirmed that carbachol acts directly on epithelial cells via muscarinic acetylcholine receptors in both, distal and proximal colon. These responses to carbachol were not influenced by inhibitors of Cl- channels situated in apical membrane (CFTRinh-172 and niflumic acid). Inhibition of basolateral influx of Cl- by serosal Ba2+ and furosemid reduced responses to carbachol in both, distal and proximal colon. Inhibitors of K+..