G cells are found deep within the pyloric glands of the stomach antrum, and occasionally in the pancreas[1] and duodenum.

Gastrin-releasing peptide is released by the post-ganglionic fibers of the vagus nerve onto G cells during parasympathetic stimulation.

Gastrin-releasing peptide, as well as the presence of amino acids in the stomach, stimulates the release of gastrin from the G cells.

Gastrin stimulates enterochromaffin-like cells to secrete histamine.

[2] Gastrin also targets parietal cells by increasing the amount of histamine and the direct stimulation by gastrin, causing the parietal cells to increase HCl secretion in the stomach.