Protective effect of 7-nitroindazole against DSP-4 induced noradrenaline depletion in mouse hippocampus

N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) is a selective noradrenaline (NA) uptake blocker, capable of inducing a long-lasting depletion of NA in some noradrenergic axon terminals originating from the locus coeruleus in rodents. Pretreatment with 7-nitroindazole, a fairly selective inhibitor of neuronal nitric oxide synthase in vivo, partially prevented DSP-4 induced NA depletion in mouse hippocampus measured seven days after the neurotoxic insult. Administration of L-arginine, the substrate of nitric oxide synthase, altered neither the NA depletion induced by DSP-4, nor the protective effect of 7-nitroindazole. Inhibition of nitric oxide synthesis by N(G)-nitro-L-arginine methyl ester did not attenuate the NA depleting effect of DSP-4. Thus, the contribution of neuronal nitric oxide synthase inhibition to the protective effect of 7-nitroindazole needs further studies. As 7-nitroindazole did not block NA uptake, this cannot play a part in the protective effect. The possible contribution of monoamine oxidase B enzyme inhibition by 7-nitroindazole to the protective effect is also discussed.