Regulation of intestinal secretion involved in the interaction between neurotransmitters and prostaglandin E2

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Abstract
In this short review, it will be described that neurotransmitter‐induced secretion in the intestine may be influenced by the tissue level of prostaglandin E2 (PGE2). In the normal condition, vasoactive intestinal polypeptide (VIP) and acetylcholine (ACh) are the predominant neurotransmitters of secretomotor neurones. VIP and ACh activate distinct second messenger systems in epithelial cells, i.e. adenosine 3′, 5′‐cyclic monophosphate (cAMP) and calcium ion (Ca2+), respectively. An increase in intracellular cAMP induces a small amount of chloride (Cl–) secretion in epithelial cells, while simultaneous increases in intracellular Ca2+ and cAMP greatly enhances the cAMP‐induced Cl– secretion. When the concentration of prostaglandins reaches a high level in the intestinal tissue substance P, which is a neurotransmitter of sensory neurones, can also induce a massive Cl– secretion by cross‐potentiation of cAMP and Ca2+ in epithelial cells. In conclusion, it is considered that the concentration of tissue PGE2 may indicate tissue alert level, and when this level elevates, PGE2 enhances ACh and SP‐induced Cl– secretion, thus mediating massive fluid secretion for host defence.