Looks like everyone has been very helpful so far on this topic!
Thanks to all!

There is only one more link I can add:

http://www.medscape.com/viewarticle/742631
Targeting N-methyl-D-aspartate Receptors for Treatment of Neuropathic Pain
Hong-Yi Zhou; Shao-Rui Chen; Hui-Lin
Expert Rev Clin Pharmacol. 2011;4(3):379-388

This receptor is very complicated....Glutamate is a main neurotransmitter in the brain, and common in the periphery as well. MSG is an inorganic man made compound that floods the body very quickly and can be very disruptive.

Glutamate is in food too, but that is thought to be bound up and slowly separated, and released slowly into the blood, compared to the MSG form.
http://www.fda.gov/Food/IngredientsP.../ucm328728.htm

My son and I both get seriously blurred vision from MSG in foods. Sometimes we'd go to lunch somewhere, and then shopping, and both of us (we are both nearsighted) would get so blurred we couldn't see anymore! Now that I have long term entrenched PN, I notice MSG really flares me.
The Bertoli dinner --Chicken Risotto.... causes burning for me at night. I've checked the ingredients, and cannot find a culprit. sigh It might be a histamine thing though. But we really like this product so we continue to buy it occasionally.

Here is a wiki on NMDA antagonists...
http://en.wikipedia.org/wiki/NMDA_receptor_antagonist

Notice Tramadol on that list.
Ketamine, clonidine, are in many compounded pain creams.
magnesium-- that is a common thing for PN here

The aspartic part of the receptor, would react with Nutrasweet, which has aspartic acid in it, and also some supplements combined with it
http://www.webmd.com/vitamins-supple...ame=aspartates
We don't see the connection to MSG and NMDA with links about aspartates, but I think it would be wise to avoid supplements containing it.

Alot of the reactions are individualistically noted as anecdotal.
It can be very painful, however, if YOU are one of the reactors, so it is best to keep an eye out for MSG or other NMDA agonists.