A recombinantly modified nonhuman mammal having central nervous system cells infected with a replication-deficient adenovirus vector comprising a gene under the control of promoter, wherein said gene has been expressed in the nervous system cells of said mammal, and said gene encodes a polypeptide molecule functioning in said cells as a neurotransmitter-synthesizing enzyme, a trophic factor, a neurotrophic factor, a growth factor, nerve growth factor or a lysosomal enzyme, or wherein said gene is an antisense sequence, the transcription product of which blocks the expression of proteins responsible for neuropsychiatric disease, of enzymes involved in the biosynthesis of said proteins or in the biosynthesis of glutamate.