Phencyclidine induces a psychotomimetic state by blocking
neurotransmission at N-methyl-D-aspartic acid (NMDA) receptors. In a
double-blind, placebo-controlled fashion, 14 medicated patients with
chronic schizophrenia were treated with glycine, a potentiator of NMDA-
receptor-mediated neurotransmission. Significant improvement in negative
symptoms occurred in the group given glycine but not in the group given
placebo, suggesting that potentiation of NMDA-receptor- mediated
neurotransmission may represent an effective treatment for
neuroleptic-resistant negative symptoms in schizophrenia.
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