Melatonin modulates TLR4/MyD88/NF-κB signaling pathway to ameliorate cognitive impairment in sleep-deprived rats

Melatonin Interplay in Physiology and Disease-The Fountain of Eternal Youth Revisited

Melatonin (N-acetyl-5-methoxytryptamine) is a hormone associated with the regulation of biological rhythms. The indoleamine is secreted by the pineal gland during the night, following a circadian rhythm. The highest plasmatic levels are reached during the night, whereas the lowest levels are achieved during the day. In addition to the pineal gland, other organs and tissues also produce melatonin, like, for example, the retina, Harderian glands, gut, ovaries, testes, skin, leukocytes, or bone marrow. The list of organs is extensive, including the cerebellum, airway epithelium, liver, kidney, adrenals, thymus, thyroid, pancreas, carotid body, placenta, and endometrium. At all these locations, the availability of melatonin is intended for local use. Interestingly, a decline of the circadian amplitude of the melatonin secretion occurs in old subjects in comparison to that found in younger subjects. Moreover, genetic and environmental factors are the primary causes of diseases, and oxidative stress is a key contributor to most pathologies. Numerous studies exist that show interesting effects of melatonin in different models of disease. Impairment in its secretion might have deleterious consequences for cellular physiology. In this regard, melatonin is a natural compound that is a carrier of a not yet completely known potential that deserves consideration. Thus, melatonin has emerged as a helpful ally that could be considered as a guard with powerful tools to orchestrate homeostasis in the body, majorly based on its antioxidant effects. In this review, we provide an overview of the widespread actions of melatonin against diseases preferentially affecting the elderly.

Enhanced Pain Sensitization Induced by Chronic Sleep Deprivation: The Role of Dopamine D2 Receptors-Dependent Homer1a Protein

Numerous studies have demonstrated a positive correlation between sleep disorders and hyperalgesia. These sleep disorders adversely affect the descending pain regulatory system. Researchers have extensively studied the midbrain dopamine system in relation to pain associated with sleep disturbances. Our study shows that chronic sleep deprivation decreases dopamine responses to noxious stimuli within the mouse nucleus accumbens, regulated by dopamine release and intracellular signals. Furthermore, we confirmed that the dopamine D2 receptors play a critical role in the pain associated with chronic sleep deprivation. Importantly, we revealed that homer1a in D2 receptor neurons enhances AMPA receptors expression.