Prostaglandins are known to affect the nervous system and can modulate synaptic transmission and neurotransmitter release, the sleep/wake cycle, fever, pain, and the immune system. Prostaglandin E2 receptor, EP1 subtype (EP1/PTGER1) is a receptor for prostaglandin E2 (PGE2). The members of the EP receptor family, EP1, EP2, EP3, and EP4, elicit their actions by altering cyclic adenosine monophosphate (cAMP) or intracellular calcium concentrations. EP1 activates phospholipase C and phosphatidylinositol turnover and stimulates the release of intracellular calcium via a Gi/Gq-coupled mechanism. EP2 and EP4 both signal through a Gs-coupled mechanism that stimulates adenylyl cyclase and increases intracellular levels of cAMP. EP1 appears to mediate the effects of PGE2 in promoting the formation of precancerous lesions in animal models of colon cancer. In addition, EP1 has an inhibitory effect on stress-induced aggressive and risk-taking behaviors in mice.