Pathophysiological implications of ASICs in gastrointestinal acid surveillance, homeostasis, sensation and pain. The graph depicts homeostatic roles of ASICs within the gastrointestinal tract (blue box) and their roles in sensation and pain mediated by primary afferent neurons (pink box). BAs, bile acids; BASIC, bile acid-sensitive ion channel; ENaCδ, epithelial Na+ channel δ subunit, LA, lactic acid; LOS, lower oesophageal sphincter; SCFAs (short chain fatty acids: acetic, butyric and propionic acid).