The transgenic construct consists of a sequence fragment encoding a consensus Kozak signal, a nuclear localization signal and cre recombinase inserted at the start codon of the mouse Nppa genomic sequence (-3 to +4 kb relative to the transcription start site). The 0.7 kb proximal regulatory region, containing the promoter and silencer and enhancer sequences, is included, as is the NRSE (neuron-restrictive silencer element) in the 3' UTR.