The mouse line was generated by homologous recombination using the CRISPR/Cas9 technology. The coding sequences for optimized FLP recombinase was inserted at the transcriptional start site of the endogenous Dbh gene replacing 106 bps of the first exon; a single lox2722 (modified LoxP) site marks the former position of a floxed neomycin resistance cassette that was deleted by Cre-mediated recombination. The resulting allele is a knock-out of Dbh protein product but express Flpo recombinase under control of the Dbh gene.