The effect of melatonin on the electron microscopic state of the lateral preoptic nucleus of the hypothalamus of rats exposed to round-the-clock lighting.

Abstract

Continuous exposure to light has been shown to disrupt circadian rhythms, leading to various physiological changes in humans. The lateral preoptic nucleus (LPO) of the hypothalamus, a key area involved in sleep-wake regulation and homeostatic processes, is sensitive to circadian alterations. Melatonin, a hormone produced by the pineal gland, is critical in maintaining circadian rhythms and is hypothesized to offer protective effects against cellular damage induced by continuous light exposure. The aim of the study. To assess the impact of melatonin on the electron microscopic structure of the lateral preoptic nucleus in rats exposed to round-the-clock lighting conditions. Materials and methods. Male white rats (n=21) were divided into three groups: a control group kept in standard 12:12 light-dark conditions, an experimental group exposed to continuous light for 7 days, and a treatment group exposed to constant light and injection of melatonin (Sigma, USA) (0.5 mg/kg body weight, intraperitoneally) daily. After the exposure period, rats were euthanized, and the LPO was extracted for electron microscopy analysis. Structural changes, including mitochondrial morphology, synaptic density, and the integrity of the nuclear envelope, were evaluated.