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 [0001]R1 and R2 are independently selected from 
hydrogen, halo, nitro, 
alkyl, acyl, alkylaryl, and XYR5; [0002]or R1 and R2, taken together, form a 5, 6, 7 or 8-membered substituted or unsubstituted carbocyclic or heterocyclic group; [0003]X and Y are independently selected from O, S, NH, and (CR6R7)n; [0004]R3 is 
hydrogen, 
alkyl or M+; M is aluminum, 
calcium, 
lithium, 
magnesium, 
potassium, 
sodium, 
zinc ion or a mixture thereof; [0005]Z is N or CR4; [0006]R4 is from selected from 
hydrogen, halo, nitro, 
alkyl, alkylaryl, and XYR5; [0007]R5 is selected from 
aryl, substituted 
aryl, heteroaryl and substituted heteroaryl; [0008]R6 and R7 are independently selected from hydrogen and alkyl; n is an integer from 1 to 6; [0009]at least one of R1, R2 and R4 is other than hydrogen; and [0010]at least one of X and Y is (CR6R7)n. D-
serine or 
cycloserine may be coadministered along with the compound of formula I.