In rodents high-dose bacterial lipopolysaccharide (LPS; 5 to 10 mg/kg), mimicking Gram-negative bacterial infection, induces robust central nervous system (CNS) inflammation, microglial-inducible nitric oxide synthase, neuronal death, blood–brain barrier breakdown and long-term cognitive decline with causative roles described for both inducible nitric oxide synthase and tumour necrosis factor (TNF)-α [13]. Here, NOS2 is linked to gram-negative bacterial infections.