Ultrastructural changes of hypothalamic nuclei under long-term influence of monosodium glutamate and its absence

Background. Monosodium glutamate (MSG) is a widely used food additive found in fast food, meat preservation, and marinating. While MSG is generally considered safe for consumption, increasing reports suggest it may have negative effects. A notable concern is the rapid weight gain associated with its appetite-stimulating effects. Hunger, satiety, and lipid metabolism are regulated by the hypothalamic nuclei. Objective. This study aims to analyze the ultrastructural changes in the components of the hypothalamic tuber cinereum following prolonged MSG exposure and its withdrawal in an experimental setting. Methods. The research material consists of ultrathin sections of the tuber cinereum from three groups of male Wistar rats weighing 218-260 g (control and two experimental groups). Material was collected after 6 weeks of MSG administration and 2 weeks after its withdrawal. Reproductive-age male rats were given MSG orally at a dose of 0.07 g/kg/day once daily via pipette. Electron microscopy was performed using a PEM-125K electron microscope to examine the ultrastructural features of the tuber cinereum under MSG exposure and withdrawal compared to control animals. Results revealed specific ultrastructural changes in the tuber cinereum. Prolonged MSG administration led to a predominance of pyramid-shaped and oval neurons with altered ultrastructure, including neuroplasmic edema, destruction of some membrane organelles, swelling and expansion of certain endoplasmic reticulum tubules, vacuolation of Golgi complex cisternae, increased numbers of vesicles and microvesicles, and reduced density of polysomes formed from ribosomes, along with partially reduced cristae in mitochondria and a cleared matrix. Conclusion. Prolonged MSG consumption causes significant ultrastructural changes in the hypothalamic tuber cinereum, and its withdrawal does not trigger sufficient compensatory processes to restore the submicroscopic organization of neural tissue.