Neuroprotective effects of 7-nitroindazole in the gerbil model of global cerebral ischaemia. 
To evaluate the role played by nitric oxide in global cerebral ischaemia we examined the effects of 7-nitroindazole and a sodium salt of 7-nitroindazole (inhibitors of neuronal nitric oxide (NO) synthase) and NG-nitro-L-arginine methyl ester (a more general inhibitor of NO synthase) in the gerbil model of cerebral ischaemia.  Four experiments were carried out.  In the first experiment, animals were either sham-operated, subjected to 5 min bilateral carotid occlusion (BCAO) or administered 7-nitroindazole or NG-nitro-L-arginine methyl ester immediately after occlusion followed by three further doses at 3, 6 and 24 h post-occlusion.  In the second experiment, we examined the effects of a sodium salt of 7-nitroindazole, which is more soluble than 7-nitroindazole, using the same protocol.  In the third experiment, the effects of the sodium salt of 7-nitroindazole administered at 10 mg/kg at 0, 3, 6, 24, 27, 30, 33, 52, 55, 72, 75 and 78 h post-occlusion or at 0.05 mg/h for 72 h via mini-pumps were evaluated.  In separate experiments, we examined the effects of three reference compounds dizocilpine (MK-801), 2, 3-dihydroxy-6-nitro-7-sulphamoyl-benz(F)-quinoxaline (NBQX) and eliprodil using the same model.  Extensive neuronal death was observed in the CA1 layer of the hippocampus in 5 min bilateral carotid occluded animals 5 days after surgery.  Both 7-nitroindazole and NG-nitro-L-arginine methyl ester provided significant neuroprotection (P < 0.01) against this neuronal death.  The sodium salt of 7-nitroindazole showed no protection when administered up to 12 times post-occlusion, but did provide significant (P < 0.01) neuroprotection when administered via mini-pump.  The neuroprotection was similar to that provided by MK-801 and eliprodil, but not as good as that observed with NBQX.  These results indicate that nitric oxide plays a role in ischaemic cell death and that selective neuronal nitric oxide synthase inhibitors can protect against ischaemic brain damage.