MSG is a neurotransmitter
that is used in the nervous system of mammals. It human, it influences the tension of the musculature
of the arteries, and thus the blood pressure.
Some ppl tend to get a migraine from it due to the contracting of the fine blood vessels in the brain.
MSG is also used as a meat tenderizer, because it influences the tension of the muscle fibrilles in, let's say, a nice piece of steak.
Annother source for the china restaurant syndrome is believed to be the cyanic acid that is contained at relatively high levels in bamboo sprout, which is a content of almost all chinese dishes.