What are the harmful effects of monosodium glutamate?

Monosodium glutamate (MSG) contains the excitatory neurotransmitter glutatamte which opens the calcium channel and triggers the neuron to fire an electrical impulse. If there is excess glutamate surrounding these neurons then they can be overstimulated generating large amounts of free radicals and inflammatory chemicals. If these neurons are overstimulated enough they will die. Even the neurons that are not killed can have permanet damage. So if large amounts of glutamte from MSG get into the brain, which it will in the areas that have no blood brain barrier, or in areas that have a defective blood brain barrier, then it can overstimulate brain cells. It has also been shown that when the blood glutamate level is high for a prolonged period that it will even seep past a supposedly intact blood brain barrier.