Melatonin and the gastrointestinal tract

Melatonin has been detected in the digestive tract of several species and a ppears to be synthesized by the enterochromaffin cells of the gut. Although a diurnal rhythm of melatonin release has been observed in gastrointestina l tissues of birds, in other species it seems to depend on the presence of nutritional elements. Melatonin binding sites have been identified in the d igestive tract of several species and it has been suggested that melatonin could act as a protecting agent of the gastrointestinal mucosa. Moreover, t he potential role of melatonin as a local regulator of gastrointestinal mot ility has been investigated. It seems that at least some effects of melaton in on gut activity depend on an antagonistic relationship between serotonin and melatonin. The effects of melatonin on segmental gut transit both in t he fasting and in the fed state, as well as on the electromyographic patter n of the small intestine in rats, are electromyographic pattern described.