Abstract: Methods for increasing D-Serine concentration and reducing concentration of the toxic products of D-Serine oxidation, for enhancing learning, memory and/or cognition, or for treating schizophrenia, Alzheimer's disease, ataxia or neuropathic pain, or preventing loss in neuronal function characteristic of neurodegenerative diseases involve administering to a subject in need of treatment a therapeutically effective amount of a compound of formula I, or a pharmaceutically acceptable salt or solvate thereof: wherein R1 and R2 are independently selected from hydrogen, halo, nitro, alkyl, acyl, alkylaryl, and XYR5; or R1 and R2, taken together, form a 5, 6, 7 or 8-membered substituted or unsubstituted carbocyclic or heterocyclic group; X and Y are independently selected from O, S, NH, and (CR6R7)n; R3 is hydrogen, alkyl or M+; M is aluminum, calcium, lithium, magnesium, potassium, sodium, zinc ion or a mixture thereof; Z is N or CR4; R4 is from selected from hydrogen, halo, nitro, alkyl, alkylaryl, and XYR5;