Table 1.

EP receptor signaling pathways and cellular localization in the normal large intestine

Receptor	Second Messenger Signal	Tissue Localization	Physiologic Role in the GI Tract
EP1^*	Phospholipase C/inositol trisphosphate	Epithelium (H), epithelium,^† glial cells, and longitudinal muscle (R)	GI tract motility (R)
EP2	Increased cAMP	Epithelium^† (R)	Chloride secretion (H)
EP3^‡	Decreased cAMP	Epithelium (H), epithelium,^† glial cells, and longitudinal muscle (R)	Duodenal bicarbonate secretion (M) and GI tract motility (R)
EP4	Increased cAMP	Epithelium and lamina propria cells (H), and epithelium^† (M and R)	Gastric mucus production (R) and chloride secretion (H)

NOTE: H, human (25 –27); M, mouse (28); and R, rat (29, 30).
↵* There are two human EP1 splice variants.
↵† mRNAs for all four EP receptors are strongly expressed by goblet cells in rat colonic epithelium (29).
↵‡ There are eight human EP3 splice variants; at least one of which mediates an increase in intracellular cAMP levels via G_s. Activation of at least two EP3 isoforms also leads to increased inositol trisphosphate levels via G_q.