Human cells isolated and/or cloned from human NT2 cells for expressing serotonin (5HT) and gamma-aminobutyric acid (GABA) are disclosed. These cells can be used as cellular minipumps to release serotonin and/or GABA to treat various neurological diseases, conditions, or disorders, particularly neurodegenerative disorders and the consequences of brain and spinal cord injuries (pain/spasticity).