A method of treating a disease in a subject in need thereof, comprising administering to the subject an effective amount of 5-O-desmethyl-omeprazole or a therapeutically acceptable salt, solvate, prodrug, or stereoisomer thereof, or a pharmaceutical composition containing 5-O-desmethyl-omeprazole, wherein the disease is selected from the group consisting of schizophrenia, schizoaffective disorder, mild cognitive impairment (MCI), Tourette Syndrome, ataxia, post-traumatic stress disorder (PTSD), dementia, loss of memory and/or cognition associated with neurodegenerative diseases, and loss of neuronal function characteristic of neurodegenerative diseases.