The Pineal Gland and Beneficial Effects of Melatonin
The pineal gland, a circumventricular organ, is involved in synchronizing the chronobiology of organisms through synthesis of melatonin. It is composed of various cell types such as pinealocytes, macrophages/microglia and astrocytes. The pinealocytes synthesize and secrete melatonin, the secretion being regulated by the environmental light/dark cycle via the suprachiasmatic nucleus. Melatonin has antioxidant, oncostatic, neuroprotective and immunoregulatory properties, some of which have been reported by recent patents. Its production is known to decline in old age and is also known to be affected by certain factors such as hypoxia-ischemia. Microglia/macrophages have a parenchymal or perivascular distribution and they may serve as a putative barrier protecting the pineal gland against entry of serum derived noxious substances. Besides their supportive role, the astrocytes in the pineal gland may release growth factors such as vascular endothelial growth factor under hypoxic conditions resulting in increased permeability of blood vessels. Our recent studies have explored the therapeutic potential of melatonin in ameliorating hypoxic damage in the brain including the pineal gland.
Keywords: Pineal gland, pinealocytes, macrophages/microglia, glutamate receptors, melatonin, hypoxia
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