GFAP expression in the spinal cord. A polyclonal antibody was used to label GFAP antigen expressing cells red. A. The spinal cord of an E18.5 Lifr +/+ untreated control mouse immunolabeled GFAP expressing cells surrounding a blood vessel in cross-section (arrow). B. Immunolabeling of a Lifr -/- control littermate of the pup in A. There are no detectable positive cells. The arrow indicates a blood vessel. C. A Lifr +/+ pup exposed to RU486. The arrows indicate positive cells associated with blood vessels. D. A Lifr -/- pup exposed to RU486 (littermate to the pup in C. The arrow indicates positive staining surrounding a blood vessel. The size bar indicates 50 μm.