This topic kind of got out of hand - almost 30 posts between my last one and now? lol. At any rate, I thought this particular thread was interesting and is beginning to touch on DAA and excitotoxicity concerns:
http://anabolicminds.com/forum/male-anti-aging/186617-anyone-low-t.html#post3119169
To respond to Easy, my thing is that I understand NMDA's MoA, and I know it's a metabolite. But you have to consider that when you ingest DAA, it's not all being taken up in the brain, it's not all being metabolized to NMDA, and it requires a certain level of NMDA to damage neurons to the point that they die. Low levels merely excite the cells (though NMDA is a potent receptor agonist, granted). So, I think you're right (easy) in saying that the final word is still unknown. Absolutely.
I guess I was just letting my opinion get the best of me, so my B.
Also, found something interesting:
http://www.ncbi.nlm.nih.gov/pubmed/20861489 Curcumin was used in this study to modulate NMDA signaling causing a knockdown of cellular Ca2+ influx. This was done I believe on tissue cultures, not people (for beyond obvious reasons). So if you're concerned about the excitotoxicity of the DAA metabolite, you could take an extra step and dose it with curcumin.