7-Nitroindazole was administered to mice by intraperitoneal injection in a dose range of 10 - 50 mg/kg. 7-Nitroindazole demonstrated anti-nociceptive effects in the late phase of the formalin-induced hind-paw licking and acetic acid-induced abdominal constriction assays; the ED50 for each assay was 27.5 and 22.5 mg/kg respectively. Maximum antinociceptive activity and NOS inhibition were detected 18-30 min following i.p. administration.

Rabbit aortic rings (with and without endothelium) were mounted for isometric tensile recording in an organ bath containing Krebs solution at 37 deg-C in an atmosphere of 5% CO2. The tissue was placed under an initial tension of 2 g and left to equilibrate for 30 - 45 minutes. Aortic rings were then precontracted with 0.2 micro-M phenylephrine. Once stable contractions were observed, cumulative concentration-effect curves were determined for 7-Nitroindazole (1 micro-M to 1 mM). Concentration-effect curves to 7-Nitroindazole were also determined in rabbit aorta after incubation with the nitric oxide synthase inhibitor L-N^G-nitro arginine p-nitroanilide (50 micro-M) for 60 minutes. The failure of acetylcholine (2 micro-M) to induce relaxation in rabbit aorta was taken as an indication of the absence of a functional endothelium. 7-Nitroindazole caused concentration-dependent relaxations in rabbit aorta with a -log EC50 of 3.67. The relaxant response to 7-Nitroindazole was not significantly different in aortic rings with or without a functional endothelium, or after pretreatment with L-N^G-nitro arginine p-nitroanilide.