Methods and devices are disclosed for the delivery of a neurotransmitter from an implanted, neurotransmitter-secreting cell culture to a target region in a subject. The cell culture is maintained within a biocompatible, semipermeable membrane which permits the diffusion of the neurotransmitter therethrough while excluding viruses, antibodies, and other detrimental agents present in the external environment from gaining access. Implantable cell culture devices are disclosed, some of which may be retrieved from the subject, replaced or recharged with new, neurotransmitter-secreting cell cultures, and reimplanted.