Fig. 3. Basal and IL-1-stimulated COX-2 mRNA expression. Dark-field photomicrographs of sections from rats killed 1 hr after intravenous injection of vehicle (top row) or 1.87 μg/kg IL-1 (bottom row), at the levels of the preoptic area (left), paraventricular nucleus (middle), and medulla (right). In vehicle-treated rats, COX-2 mRNA is evident throughout the isocortex, hippocampal formation, and the area postrema. Some signal is also clearly evident within the meninges (men) and a few blood vessels (bv). IL-1 treatment does not appear to alter neuronal expression of COX-2 mRNA, although expression by cells associated with the vasculature and the meninges is clearly increased throughout the brain. Scale bar, 100 μm. ac, Anterior commissure; och, optic chiasm; men, meninges; OT, olfactory tubercule; CP, caudate putamen; Pir, piriform cortex; iso, isocortex;DG, dentate gyrus; CA3, field CA3 of ammon's horn; NLOT, nucleus of lateral olfactory tract;AP, area postrema; cc, central canal;SNV, spinal nucleus of trigeminal.