Cholinergic inhibition of electrogenic sodium absorption in the guinea pig distal colon.
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.
Hayashi
Hisayoshi
H
Laboratory of Physiology, School of Food and Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
Suzuki
Tomoko
T
Yamamoto
Takeshi
T
Suzuki
Yuichi
Y
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
D018679:Cholinergic Agonists; D002800:Cholinesterase Inhibitors; D015222:Sodium Channels; D012979:Sodium Radioisotopes; D002217:Carbachol; D012964:Sodium; D010830:Physostigmine; D000109:Acetylcholine; D002118:Calcium