title: Cholinergic inhibition of electrogenic sodium absorption in the guinea pig distal colon.
abstract: Submucosal cholinergic and noncholinergic neurons in intestines have been shown to be involved in regulating epithelial transport functions, particularly stimulating Cl(-) secretion. This study investigates the role of submucosal cholinergic neurons in regulating electrogenic Na(+) absorption in distal colon. Amiloride-sensitive short-circuit current (I(sc)) and (22)Na(+) flux were measured in mucosal and mucosal-submucosal preparations mounted in Ussing chambers. In the mucosal preparation, carbachol (CCh) added to the serosal side inhibited amiloride-sensitive I(sc) and amiloride-sensitive (22)Na(+) absorption. The inhibitory effect of CCh was observed at approximately 0.1 microM, and maximum inhibition of approximately 70% was attained at approximately 30 microM (IC(50) = approximately 1 microM). CCh-induced inhibition of amiloride-sensitive I(sc) was almost totally abolished by 10 microM atropine. Treatment of the tissue with ionomycin markedly reduced amiloride-sensitive I(sc), but a subsequent addition of CCh further decreased it. Also, CCh still had an inhibitory effect, although significantly attenuated, after the tissue had been incubated with a low-Ca(2+) solution containing ionomycin and BAPTA-AM. Applying electrical field stimulation to submucosal neurons in the mucosal-submucosal preparation resulted in inhibition of amiloride-sensitive I(sc), approximately 33% of this inhibition being atropine sensitive. Physostigmine inhibited amiloride-sensitive I(sc), this effect being abolished by atropine. In conclusion, submucosal cholinergic and noncholinergic neurons were involved in inhibiting electrogenic Na(+) absorption in colon. This inhibition by cholinergic neurons was mediated by muscarinic receptor activation.
authors.affiliation: Laboratory of Physiology, School of Food and Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Hayashi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Suzuki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D002799:Cholinergic Fibers / Q000502:physiology*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003106:Colon / Q000294:innervation* / Q000378:metabolism*; D004558:Electric Stimulation; D017615:Enteric Nervous System / Q000502:physiology*; D006168:Guinea Pigs; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology; D008297:Male; D010830:Physostigmine / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D012979:Sodium Radioisotopes
chemical_list: D018679:Cholinergic Agonists; D002800:Cholinesterase Inhibitors; D015222:Sodium Channels; D012979:Sodium Radioisotopes; D002217:Carbachol; D012964:Sodium; D010830:Physostigmine; D000109:Acetylcholine; D002118:Calcium