NOS2 and viral infectious disease: The thirdisoform, (3) inducible NOS (iNOS), is expressed only when cells arestimulated, often by immune and inflammatory responses to an invadingpathogen.37 Within the normal brain, eNOSand nNOS are constitutively expressed whereas in the context of iNOS,its increased expression within the CNS is proposed to be pathological.38 Thus, iNOS could play a key role in the relationshipbetween viral infection and neuronal function.