Makoto Yoshimura1, Takashi Mikami1, Kayuri Kuroda1, Maki Nishida1, Kazuma Ito1, Anupom Mondal1, Kouhei Koyama1, Takamichi Jogahara2, Ichiro Sakata1, Takafumi Sakai3. 1. Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan. 2. Laboratory of Animal Management and Resources, Department of Zoology, Faculty of Science, Okayama University of Science, Okayama, 700-8525, Japan. 3. Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan. tsakai@mail.saitama-u.ac.jp.
Abstract
BACKGROUND: Gastric acidification inhibits motilin-induced gastric phase III contractions. However, the underlying mechanism has not been thoroughly investigated. Here, we studied the inhibitory mechanism by gastric acidification on motilin-induced contraction in Suncus murinus (S. murinus). METHODS: We measured interdigestive gastric phase III contractions in conscious, freely moving S. murinus, and examined the inhibitory effect of gastric acidification on motilin action and the involvement of the vagus nerve and transient receptor potential vanilloid receptor 1 (TRPV1) in the inhibitory mechanism. RESULTS: A bolus injection of motilin evoked phase III-like contractions during intravenous infusion of saline. Intragastric acidification (pH 1.5-2.5) inhibited motilin-induced phase III contractions in a pH-dependent manner and significantly decreased the motility index at a pH below 2.0. In contrast, intraduodenal acidification (pH 2.0) failed to inhibit motilin-induced contractions. Vagotomy significantly alleviated the suppression of motilin-induced gastric contractions under acidic conditions (pH 2.0), suggesting vagus nerve involvement. Moreover, intragastric acidification (pH 2.0) significantly increased the number of c-Fos-positive cells in the nucleus tractus solitarii. In vagotomized S. murinus, the number of c-Fos-positive cells did not change, even under gastric acidification conditions. TRPV1 mRNA was highly expressed in the muscle and mucosal regions of the antrum and the nodose ganglion, whereas was not detected in the upper small intestine. Capsazepin, a TRPV1 antagonist, completely rescued the inhibitory effect of gastric acidification. CONCLUSIONS: Gastric acidification in S. murinus inhibits motilin-induced contractions, a finding similar to results observed in humans, while TRPV1-expressing vagus nerves play a role in the inhibitory mechanism.
BACKGROUND: Gastric acidification inhibits motilin-induced gastric phase III contractions. However, the underlying mechanism has not been thoroughly investigated. Here, we studied the inhibitory mechanism by gastric acidification on motilin-induced contraction in Suncus murinus (S. murinus). METHODS: We measured interdigestive gastric phase III contractions in conscious, freely moving S. murinus, and examined the inhibitory effect of gastric acidification on motilin action and the involvement of the vagus nerve and transient receptor potential vanilloid receptor 1 (TRPV1) in the inhibitory mechanism. RESULTS: A bolus injection of motilin evoked phase III-like contractions during intravenous infusion of saline. Intragastric acidification (pH 1.5-2.5) inhibited motilin-induced phase III contractions in a pH-dependent manner and significantly decreased the motility index at a pH below 2.0. In contrast, intraduodenal acidification (pH 2.0) failed to inhibit motilin-induced contractions. Vagotomy significantly alleviated the suppression of motilin-induced gastric contractions under acidic conditions (pH 2.0), suggesting vagus nerve involvement. Moreover, intragastric acidification (pH 2.0) significantly increased the number of c-Fos-positive cells in the nucleus tractus solitarii. In vagotomized S. murinus, the number of c-Fos-positive cells did not change, even under gastric acidification conditions. TRPV1 mRNA was highly expressed in the muscle and mucosal regions of the antrum and the nodose ganglion, whereas was not detected in the upper small intestine. Capsazepin, a TRPV1 antagonist, completely rescued the inhibitory effect of gastric acidification. CONCLUSIONS: Gastric acidification in S. murinus inhibits motilin-induced contractions, a finding similar to results observed in humans, while TRPV1-expressing vagus nerves play a role in the inhibitory mechanism.
Entities:
Keywords:
Gastric acidification; Motilin; Phase III contraction; TRPV1; Vagus nerve
Authors: Marion Danzer; Milana Jocic; Claudia Samberger; Evelin Painsipp; Elisabeth Bock; Maria-Anna Pabst; Karl Crailsheim; Rudolf Schicho; Irmgard T Lippe; Peter Holzer Journal: Am J Physiol Gastrointest Liver Physiol Date: 2003-10-30 Impact factor: 4.052