Melatonin, its agonists in pain modulation: clinical application

Melatonin (N-acetyl-5-methoxytryptamine) is a hormone secreted by the pineal gland of all animals as well as in human beings. It is not only synthesized in the pineal gland but also many other organs like eye (Cardinali and rosner, 1971), gastro-intestinal tract (Bubenik, 2002), skin (Slominiski, 2005), lymphocytes (Carrillo-Vico et al., 2004), thymus (Naranjo et al., 2007) etc. Besides being acting as a hormone regulating reproductive functions of the body (Srinivasan et al., 2008), it participates in many other important functions of the body like immune regulation (Maestroni et al., 1988; Srinivasan et al., 2008), prevention of cancer (Hill and Blask, 1988), control of circadian rhythms (Armstrong, 1989) and sleep regulation (Tzischinsky et al., 1994; Zhdanova et al., 1995). Since melatonin is secreted at high concentrations during dark periods of the night-hours it is referred as “the chemical code of darkness” (reiter, 1991). Number of animal studies has shown that pain perception is circadian in nature (Pilcher et al., 1982; Melatonin, its agonists in pain modulation: clinical application