Related Experiment Video
Updated: Aug 7, 2026

Profiling Luminal pH in Three-Dimensional Gastrointestinal Organoids Using Microelectrodes
Published on: July 5, 2024
Luminal amino acid sensing in the rat gastric mucosa
Hisayuki Uneyama1, Akira Niijima, Ana San Gabriel
1Physiology and Nutrition Group, Institute of Life Sciences, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki 210-8681, Japan. hisayuki_uneyama@ajinomoto.com
Abstract:
Recent advancements in molecular biology in the field of taste perception in the oral cavity have raised the possibility for ingested nutrients to be "tasted" in the upper gastrointestinal tract. The purpose of this study was to identify the existence of a nutrient-sensing system by the vagus in the rat stomach. Afferent fibers of the gastric branch increased their firing rate solely with the intragastric application of the amino acid glutamate. Other amino acids failed to have the same effect. This response to glutamate was blocked by the depletion of serotonin (5-HT) and inhibition of serotonin receptor(3) (5-HT(3)) or nitric oxide (NO) synthase enzyme. Luminal perfusion with the local anesthesia lidocaine abolished the glutamate-evoked afferent activation. The afferent response was also mimicked by luminal perfusion with a NO donor, sodium nitroprusside. In addition, the NO donor-induced afferent activation was abolished by 5-HT(3) blockade as well. Altogether, these results strongly suggest the existence of a sensing system for glutamate in the rat gastric mucosa. Thus luminal glutamate would enhance the electrophysiological firing rate of afferent fibers from the vagus nerve of the stomach through the production of mucosal bioactive substances such as NO and 5-HT. Assuming there is a universal coexistence of free glutamate with dietary protein, a glutamate-sensing system in the stomach could contribute to the gastric phase of protein digestion.
Related Concept Videos
Stomach pH Regulation
The acid-secreting gastric mucosal epithelial cells (parietal cells) lining the stomach lumen maintain the low pH in the lumen. Numerous ion transporters and channels on these parietal...
Mucosal Barrier of the Stomach
Within parietal cells, carbonic acid is first formed through the reaction of water and carbon dioxide. The dissociation of carbonic acid releases bicarbonate and hydrogen ions. The bicarbonate...
G-Protein Gated Ion Channels
Sensory organs,...
Intestinal Phase of Digestion
The arrival of the chyme in the small intestine distends the duodenum, which triggers the enterogastric reflex. This distension...
Hormonal Regulation
Neural Regulation

