Microglia Depletion by CSF1R Inhibition

Animals received subcutaneous injections of BLZ (MW: 398.48, MedChem Express HY-12768/CS-3971), a small molecule inhibitor of CSF1R^{16 (link)}, dissolved in dimethylsulfoxide (DMSO; D136-1; Fisher Scientific) to eliminate microglia as previously described^{9 (link)}. Injections of 0.01 ml of BLZ solution (200 mg/kg) or control (DMSO) were administered subcutaneously every 2 or 3 days, depending on treatment group, starting from P2 with the last injection delivered at P12 or P15. Groups receiving an additional CSF1R inhibitor were fed a diet containing PLX5622 (PLX) or the respective control rodent diet ad libitum (provided by Plexxikon Inc. and formulated in AIN-76A standard chow by Research Diets Inc, 1200 mg/kg chow)¹⁷ . Litters were given PLX or the respective control (CTL) through the milk of the lactating mother. The mother was given PLX or CTL when the litter was P2, the same day that BLZ945 or DMSO injections were administered to pups. The mother remained on the chow until the litter was of age to wean (P21), and pups had access to the PLX or control chow when they began a solid diet (~ P16). After weaning, BLZ/PLX treated mice remained on the PLX chow until testing at either 4 or 7 weeks of age.