Background strain: Long-Evans rat (Iar:Long-Evans, RGD:18337282). This strain was established by injection of modified BAC (cre gene was inserted into the exon 2 of rat Tac1 gene) into Long-Evans rat's fertile eggs. This transgenic strain expresses Cre recombinase under the control of Tac1 promoter. The expression levels of Cre recombinase in LE-Tg(Tac1-cre)6-7Koba are lower than in LE-Tg(Tac1-cre)4-1Koba (RGD:38599247)