• Thomas Wultsch, Evelin Painsipp, Anaid Shahbazian, Martina Mitrovic, Martin Edelsbrunner, Michel Lazdunski, Rainer Waldmann, and Peter Holzer.
• Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UNSA UMR 6097, Sophia Antipolis, Valbonne, France.
• Pain. 2008 Feb 1; 134 (3): 245-253.

AbstractGastric acid challenge of the rat and mouse stomach is signalled to the brainstem as revealed by expression of c-Fos. The molecular sensors relevant to the detection of gastric mucosal acidosis are not known. Since the acid-sensing ion channels ASIC2 and ASIC3 are expressed by primary afferent neurons, we examined whether knockout of the ASIC2 or ASIC3 gene modifies afferent signalling of a gastric acid insult in the normal and inflamed stomach. The stomach of conscious mice (C57BL/6) was challenged with intragastric HCl; two hours later the activation of neurons in the nucleus tractus solitarii (NTS) of the brainstem was visualized by c-Fos immunocytochemistry. Mild gastritis was induced by addition of iodoacetamide (0.1%) to the drinking water for 7 days. Exposure of the gastric mucosa to HCl (0.25M) caused a 3-fold increase in the number of c-Fos-positive neurons in the NTS. This afferent input to the NTS remained unchanged by ASIC3 knockout, whereas ASIC2 knockout augmented the c-Fos response to gastric HCl challenge by 33% (P<0.01). Pretreatment of wild-type mice with iodoacetamide induced mild gastritis, as revealed by increased myeloperoxidase activity, and enhanced the number of NTS neurons responding to gastric HCl challenge by 41% (P<0.01). This gastric acid hyperresponsiveness was absent in ASIC3 knockout mice but fully preserved in ASIC2 knockout mice. The current data indicate that ASIC3 plays a major role in the acid hyperresponsiveness associated with experimental gastritis. In contrast, ASIC2 appears to dampen acid-evoked input from the stomach to the NTS.

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