Melatonin and Its Therapeutic Potential in Neuroprotection

Melatonin, a neurohormone synthesized and secreted by the pineal gland, has antioxidant, immunoregulatory and neuroprotective actions. Production of melatonin is regulated by light and darkness, light decreasing whereas darkness increasing it. Production of melatonin is also known to decline in old age and under hypoxic-ischemic conditions. Melatonin is considered as body's chronological pacemaker and has a wide array of useful applications. It has been used in the treatment of sleep disorders and is reported to have neuroprotective effects in many central nervous system (CNS) conditions such as amyotrophic lateral sclerosis, Parkinson's disease, Alzheimer's disease, ischemic injury, neuropsychiatric disorders and head injury. It suppresses oxidative damage in the retina in ocular pathologies and reduces retinal ganglion cell death. It affords protection to the blood-brain and blood-retinal barriers in hypoxic conditions by suppressing the production of vascular endothelial growth factor and nitric oxide which are known to increase vascular permeability. Protective effects of melatonin against hypoxic damage have been demonstrated in newborn experimental animals where it suppressed damage in many parts of the brain such as the hippocampus and choroid plexus in lateral ventricles. Along with this, exogenous administration of melatonin in newborn animals has been shown to be effective in enhancing the surface receptors and antigens on the macrophages/microglia in the CNS supporting its immunoregulatory actions.