Cholinergic regulation of guinea pig duodenal bicarbonate secretion

H. S. Odes, R. Muallem, R. Reimer, W. Beil, M. Schwenk, K. F. Sewing

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23 Scopus citations

Abstract

Although it is well known that vagal stimulation induces duodenal HCO3/- secretion, there is presently no information about the nature of the cholinoceptor and the intracellular signals involved. In a series of experiments performed in a guinea pig duodenal loop model in situ, intravenous carbachol, atropine, pirenzepine, and hexamethonium were used to determine the extent of cholinergic stimulation and the types of cholinoceptors. Carbachol (2 μg · kg-1 · 5 min-1) stimulated HCO3/- secretion threefold, and atropine (0.1 mg · kg-1 · 5 min-1) and pirenzepine (1 mg · kg-1 · 5 min-1) both abolished this effect. In addition, hexamethonium (0.3 mg · kg-1 · 5 min-1) inhibited carbachol- stimulated duodenal HCO3/- secretion. Vasoactive intestinal peptide (VIP, 5 μg · kg-1 · 5 min-1) stimulated duodenal HCO3/- secretion, and this action was partly inhibited by atropine (0.1 mg · kg-1 · 5 min-1) but not by pirenzepine (1 mg · kg-1 · 5 min-1). [4Cl-D-Phe6,Leu17]VIP (3.3 mg/kg), an antagonist to VIP, reduced basal, VIP-stimulated, and carbachol-stimulated HCO3/- secretion. To examine the role of Ca2+ in this process, Ca2+ ionophore A23187, verapamil, and nifedipine were employed. A23187 (5, 50, 500 μg · kg-1 · 5 min-1) stimulated duodenal HCO3/- secretion, an effect blocked by the VIP antagonist, and modestly augmented the effect of carbachol. Verapamil (0.2 mg · kg-1 · 5 min-1) and nifedipine (1.7 mg · kg-1 · 5 min-1) stopped the effect of carbachol on duodenal HCO3/- secretion. These results suggest, that in cholinergic regulation of duodenal HCO3/- secretion, the M-cholinoceptor pathway, Ca2+, and VIP are involved.

Original languageEnglish
Pages (from-to)G270-G276
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume265
Issue number2 28-2
DOIs
StatePublished - 1 Jan 1993
Externally publishedYes

Keywords

  • M-cholinoceptor agonists
  • M-cholinoceptor antagonists
  • [4Cl-D- Phe,Leu]vasoactive intestinal peptide
  • calcium ionophore A23187
  • hexamethonium
  • nifedipine
  • vasoactive intestinal peptide
  • verapamil

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