Central Nervous System (CNS)

Functionally, the CNS consists of a sensory and motor system, and both usually collaborate with each other for proper functions. Structurally, it consists of the brain located in the cranial cavity and the spinal cord located in the vertebral canal. Generally, the brain occupies approximately 2% of the total body weight. It expends approximately 20% of the total oxygen inhaled through the respiratory system and expends roughly 25% of the D-glucose ingested through the GI system. Thus, the brain is one of the organs generating oxygen free radicals most vigorously so that some apparatus for its protection from oxidative damages should be inevitable. The organ containing the highest concentration of vitamin C in the body is the brain. The average concentration of vitamin C in the human peripheral blood is approximately 40~60 μM. However, its concentration in the neuronal cytoplasm reaches approximately 10 mM, about 200 times as high as the human serum concentration. The cytoplasmic concentration of vitamin C in astrocytes or microglial cells, which usually consume 20% of the total amount of oxygen neurons consume, is about 1~2 mM suggesting that the concentration of vitamin C in brain cells seems to be closely related to the consumption amount of oxygen. Vitamin C may play a critical role in CNS development, especially in the development of the cerebellum. Additionally, we also observed defects in motor function upon vitamin C deficiency. We presented morphological evidence for the defects in motor function with atrophic changes of the granule cells and Purkinje cells in the adult cerebellum of Gulo(−/−) mice upon vitamin C deficiency. Conclusively, vitamin C deficiency during gestation may induce intraparenchymal hemorrhages and severe defects in the development of the cerebellum. Several neurodegenerative disorders such as Alzheimer disease, Parkinson disease, and Huntington disease are known to be closely related with ROS in terms of their pathogenesis. Dementia is a general designation of mental deterioration. Parkinson disease is a slowly progressive disease characterized by several motor dysfunctions such as a masklike face, a characteristic tremor of the resting muscles, a slowing of voluntary movements, a festinating gait, a peculiar posture, and weakness of the muscles. Considering again the relationship between the oxygen consumption proportion (20%) of neurons and the extremely high concentration of vitamin C (10 mM) in the neuronal cytoplasm, oxidative stress seems to have an essential role in this disease process.