A-F, FAAH (A-C, E) and GFAP (D) immunoreactivities in parahippocampal cortex and FAAH activity in neuritic plaques (F). A, FAAH staining in a healthy individual sample. Note the neuronal pattern of staining (inset). B, Low and high (inset) magnifications of FAAH immunoreactivity in parahippocampal cortex of an AD case. Note the intense signal for FAAH in hypertrophied astrocytes surrounding neuritic plaques. C, Detail of FAAH immunoreactivity in hypertrophied astrocytes. D, Low and high (inset) magnification of GFAP immunoreactivity in an AD case. Note that the signal is detectable in both protoplasmic and fibrous (arrow) astrocytes. E, FAAH staining after preabsorption and coincubation of the antibody with the immunizing peptide. Note the absence of any detectable signal. F, FAAH activity. Individual plaques were dissected under microscope, homogenized, and assayed for FAAH activity using the conversion of [14C]AEA to [14C]ethanolamine during a 15 min incubation. Shown is the mean of five individual determinations; groups were significantly different using unpaired t tests with p < 0.05. Scale bars: A, B, D, 800 μm; E, inset in A, 400 μm; insets in B and D, 200 μm; C, 100 μm.