title: Differential effect on neuropeptide release of different concentrations of hydrogen ions on afferent and intrinsic neurons of the rat stomach.
abstract: In the muscle layer of the glandular portion of the rat stomach, in vivo capsaicin pretreatment markedly reduced calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) but did not affect substance P-like immunoreactivity (SP-LI). Accordingly, in vitro superfusion of slices of this tissue with capsaicin (10 mumol/L) released CGRP-LI but not SP-LI, whereas both neuropeptides were released by 80 mmol/L K+. Exposure to relatively low-pH (pH 6) physiological salt solution induced an increase in the CGRP-LI outflow that was reduced by 70% in a Ca(2+)-free medium and was completely abolished by a previous exposure to capsaicin. However, superfusion with pH-6 medium did not produce any detectable SP-LI release. After exposure to pH-6 medium, both capsaicin and high-K+ medium were still able to release a consistent quantity of CGRP-LI and SP-LI, respectively. Increased mucosal blood flow induced by acid back-diffusion is considered a protective mechanism against mucosal gastric lesion. The present findings suggest that hydrogen ions diffusing into the gastric wall may promote protective vasodilatation by activating the "efferent" function of capsaicin-sensitive nerves without affecting the secretory process of other intrinsic peptidergic neurons.
authors.affiliation: Gastroenterology Unit, University of Florence, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Geppetti
authors.forename: M
authors.initials: M
authors.lastname: Tramontana
authors.forename: S
authors.initials: S
authors.lastname: Evangelista
authors.forename: D
authors.initials: D
authors.lastname: Renzi
authors.forename: C A
authors.initials: CA
authors.lastname: Maggi
authors.forename: B M
authors.initials: BM
authors.lastname: Fusco
authors.forename: E
authors.initials: E
authors.lastname: Del Bianco
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology; D003470:Culture Media / Q000494:pharmacology; D005753:Gastric Mucosa / Q000098:blood supply / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000294:innervation* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D011522:Protons; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013270:Stomach / Q000294:innervation*; D013373:Substance P / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects
chemical_list: D003470:Culture Media; D011522:Protons; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide; D011188:Potassium; D002211:Capsaicin