Histopathological changes and GFAP immunohistochemistry. A Vacuolation was graded 0–5 in nine defined brain areas (modified from Fraser and Dickinson 1968): 1, rostral part of medulla oblongata at the level of the obex; 2, transverse section of cerebellar cortex; 3, dorsal grey substance of the superior colliculus; 4, hypothalamus; 5, thalamus: massa intermedia and central nuclei; 6, hippocampus; 7, septal nuclei; 8, cerebral cortex dorsal to corpus callosum; and 9, cerebral cortex dorsal to septal nuclei. B GFAP signals were scored from 0 to 3 in thalamus and in three layers of the hippocampus (ML, molecular layer; SGZ, sub-granular zone; and hilus). C Vacuoles were primarily located in the neuropil of grey matter. Pictures show a representative vacuolation score 4 (PRNP+/+) and score 5 (PRNP+/Ter) in the thalamus. D Astrocyte GFAP labeling displayed increased length and thickening of primary and secondary processes in the thalamus of some scrapie-positive animals (goat #417 and #527). Values are mean ± SEM. n = 12 (4 PRNP+/+, 4 PRNP+/Ter, and 4 PRNPTer/Ter). Magnification: C, D ×200.