ABSTRACT
Melatonin (5-methoxy-N-acetyltryptamine) was rst isolated and discovered by Lerner and coworkers in the late 1950s (Lerner et al., 1960). In vertebrates, the synthesis of melatonin takes place primarily in the pineal gland and the retina, as the synthesis and release of melatonin show a marked circadian variation, being at higher levels during the night and at lower levels during the day (Tosini and Menaker, 1998). While it is well established that melatonin is a major regulator of circadian rhythm, abundant evidence suggests that this hormone may be involved in the regulation of a variety of physiological processes, such as sleep, reproduction, immune and vascular response, etc. (Hardeland et al., 2011). In recent years, it has been demonstrated that melatonin may modulate the function of various types of neurons in the central nervous system (CNS) by modifying the activity of ligand-and voltage-gated ion channels (Yang et al., 2011a). These actions of melatonin on central neurons are mediated by distinct intracellular pathways via the activation of different subtypes of melatonin receptors (Huang et al., 2013).
