For -galactosidase
(-gal) staining, free-floating sections were stained for 16
hours with a solution consisting of phosphate buffered saline
(PBS) with .1 mol/L potassium ferricyanide, .1 mol/L potassium
ferrocyanide, 1 mol/L MgCl2, and 1 mg/mL X-gal in dimethylformamide
(all from Sigma, St. Louis, Missouri).