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“Excitotoxicity resulting from excessive activation of NMDA receptors may enhance the localized vulnerability of neurons in a manner consistent with AD neuropathology, as a consequence of an altered regional distribution of NMDA receptor subtypes. This review discusses mechanisms for the involvement of the NMDA receptor complex and its interaction with polyamines in the pathogenesis of AD. NMDA receptor antagonists have potential for the therapeutic amelioration of AD.”

“Growing evidence links glutamate excitotoxicity to various neurodegenerative diseases as cerebral ischemia, epilepsy, Alzheimer’s disease, Parkinsons’ disease and multiple sclerosis. In addition, several environmental pollutants result in excessive glutamatergic neurotransmission and may eventually lead to neurodegenerative diseases.”

“As our knowledge of the pathophysiology and biochemistry of the neurodegenerative diseases increases, the connection to excitotoxicity has become stronger.(21) This is especially so with the interrelationship between excitotoxicity and free radical generation and declining energy production with aging. Several factors of aging have been shown to magnify this process. For example, as the brain ages its iron content increases, making it more susceptible to free radical generation. Also, aging changes in the blood brain barrier, microvascular changes leading to impaired blood flow, free radical mitochondrial injury to energy generating enzymes, DNA adduct formation, alterations in glucose and glutamate transporters and free radical and lipid peroxidation induced alterations in the neuronal membranes all act to make the aging brain increasingly susceptible to excitotoxic injury. Over a lifetime of free radical injury due to chronic stress, infections, trauma, impaired blood flow, hypoglycemia, hypoxia and poor antioxidant defenses secondary to poor nutritional intake, the nervous system is significantly weakened and made more susceptible to further excitotoxic injury. We know that a loss of neuronal energy generation is one of the early changes seen with the neurodegenerative diseases. This occurs long before clinical disease develops. But, even earlier is a loss of neuronal glutathione functional levels.”