NDMA-receptors - stimulate or antagonise? That's the question.
Normal stimulation is essential for learning (and probably other
processes), but excessive stimulation is produces seizures and
neurotoxicity (excitotoxicity), which is the theoretical basis for the
MSG (monosodium glutamate) controversy, and some of the
Potent NMDA-antagonists (PCP, ketamine) have been associated
with symptoms resembling schizophrenia, and with neurotoxicity,
but ketamine has also been shown to have exceptionally potent
Weaker NMDA-antagonists (memantine, amantadine) have not
been associated with neurotoxicity - on the contrary there is some
evidence that they may have neuroprotective properties.
Amantadine has anti-parkinsonian effects, and may boost the
effects of antidepressants - probably the same applies to
memantine. Amantadine has also been used to reduce the side
effects of anti-psychotics.
My personal experience with memantine is brief. After some initial
adverse effects, I found some temporary relief of anhedonia. I'm
interested in trying it again some time.
I have more experience with amantadine, but I noticed no effects
worth mentioning, even after combinations with various other