Supraphysiological levels of D-serine will not activate the NMDA receptor in a vacuum/alone/by itself. It requires the criteria I listed previously prior to activation (co-agonism, receptor upstream activation, intracellular depoarlization).
This I fully understand, but thank you for clarifying

It's NOOTROPIC (notice the capital letters? I can be an petulant child too) modality is secondary to its pharmacodynamic characteristics: higher potency. Potency means that it can produce a given effect at a lower concentration to the same degree as another compound requiring a higher concentration. Hopefully you can peice together the context from here (i.e. D-serine vs. glycine).
Firstly, in the spirit of keeping things
positive I am going to ignore
this:
"It's NOOTROPIC (notice the capital letters? I can be an petulant child too)..." 
Secondly, thank you kindly for your reply. However, I am still somewhat confused (which is almost certainly down to my misunderstanding something as opposed to any error on your part); hence, if you can be kind enough to help clarify matters I would very much appreciate it.

I understand that there exists a lengthy list of criteria all of which must be fulfilled in order for D-SERINE to activate the NMDA RECEPTOR.
On the one hand this is good news, because this means that not only is there little possibility of someone who suffers a pre-existing state of NMDA RECEPTOR OVERSTIMULATION (such as those with CNS LYME, MS, HUNTINGTON'S, PARKINSON'S etc..) exacerbating the situation by supplementing with D-SERINE; but also, there is little possibility of healthy individuals
inducing NMDA RECEPTOR OVERSTIMULATION by doing so, which would be equally undesirable. In short, good news for everyone!

However, on the other hand, it is my understanding that in order for D-SERINE to exert its NOOTROPIC effect the activation of the respective NMDA RECEPTOR is a necessity... your colleague kindly clarified this earlier, nicely and succinctly:
D-Serine is an NMDA receptor agonist, specifically at the glycine binding site. This is it's main nootropic MOA.
And hence, because there exists a lengthy list of criteria, all of which must be fulfilled in order for D-SERINE to activate the NMDA RECEPTOR, doesn't that mean that unless all those criteria are fulfilled, and consequently said NMDA RECEPTOR is activated, D-SERINE won't in fact exert any NOOTROPIC effect?

In which case, to clarify, when taking supplemental D-SERINE specifically seeking to attain its NOOTROPIC effect, does this mean that one would need to deliberately ensure that
all those criteria
are fulfilled?
And if this is indeed the case, wouldn't
the timing of when all the respective criteria are fulfilled be similarly vital? In that specifically it would be important to ensure that all the criteria are fulfilled specifically at the time at which the D-SERINE is absorbed fully into the bloodstream and hits peak plasma levels, as opposed to when you swallow it?
If so, then the time taken for D-SERINE to achieve PEAK PLASMA LEVEL following PER ORAL administration would be a vital piece of information... In which case, do you happen to know what it is?

RE: POTENCY - Thank you for clarifying this, but I do know what potency is; and surely potency only becomes a relevant factor if all the criteria are fulfilled for D-SERINE to activate the respective NMDA RECEPTOR and hence exert its NOOTROPIC effect? Please do not hesitate to correct me if I am wrong
Edited by ScienceGuy, 01 September 2012 - 10:23 AM.