Expression of iNOS and COX-2 mRNA in iNOS null mice and C57BL/6 controls after occlusion of the MCA. iNOS and COX-2 mRNA was determined in the ischemic brain by RT-PCR. Porphobilinogen deaminase mRNA, a ubiquitously expressed sequence, was coamplified and used as internal standard. MCA occlusion induces iNOS mRNA in the ischemic brain in C57BL/6 mice but not in iNOS null mice (A). MCA occlusion up-regulates COX-2 mRNA expression in the ischemic brain of iNOS null mice and C57BL/6 mice (B). The time course of COX-2 up-regulation is comparable in C57BL/6 mice (C) and iNOS null mice (D). B6, C57BL/6; iNOS −/−, iNOS null mice; OD, optical density; bl, blank (sample without the reverse transcriptase step); c, contralateral; s, stroke; std, standards; PBD, porphobilinogen deaminase.