A combined EF1a-tTA and TetO-mCh/Rs1 transgene in a single construct (separated by a 2A ribosomal skip site) was inserted in the Gt(ROSA)26Sor locus. Rs1 is an engineered Gs-coupled G-protein coupled receptor in which an aspartic acid to alanine amino acid residue change at position 100 was made to generate serotonin-insensitive GPCR. (J:193162)