There is good evidence that the glutamate system is abnormal in schizophrenia. In short, the glutamate theory of schizophrenia proposes that underactive NMDA receptor activity leads to excess glutamate release in the front portion of the brain. In this video, a functional neurologist mentions that glutamate-regulated excitotoxicity may contribute to brain volume reductions observed in patients with schizophrenia. Jump to frame 15:59 the video.
Concerning sarcosine, I was told by one doctor that prophylactic ‘preconditioning’ with sarcosine may promote resistence to injury of neurons associated with glutamate hyperexcitability, by inducing brain tolerance.
For those of you who don’t know, brain tolerance is a protective mechanism induced by a preconditioning substance, which prepare the tissue against harmful insults.