CreERT2-mediated recombination within the adult hippocampus depends on the transgene copy number and the tamoxifen dose. Pyramidal neurons in the hippocampal CA1 region of GRCaMKCreERT2 and control animals were analyzed by immunohistochemistry on vibratome-sections using an antibody against GR. Mice were injected with tamoxifen for five consecutive days either once per day (5 mg) (A, C, E, G) or twice per day (10 mg) (B, D, F, H) and sacrificed ten days after the last injection. Treatment with 5 mg tamoxifen results in an incomplete loss of GR protein if one or two copies of the CaMKCreERT2 transgene are present (C, E), whereas four copies of the transgene are sufficient to induce complete GR protein loss (G). GRCaMKCreERT2 mice harboring two or four copies of the Cre transgene display complete loss of GR protein after injection of 10 mg tamoxifen (F, H). A visible but still incomplete loss of GR protein was seen in CaMKCreERT2 transgenic mice of the one-copy line treated with 10 mg tamoxifen (D) whereas tamoxifen-treated controls show no apparent loss of GR (A, B).
Erdmann et al. BMC Neuroscience 2007 8:63 doi:10.1186/1471-2202-8-63