Co-expression of APP with cNOS but not iNOS after cortical injury in rat

Alterations in the expression of both the beta-amyloid precursor protein (APP) and nitric oxide synthase (NOS) might be involved in neurodegenerative conditions and/or in the neuronal response to injury. We have investigated the relationship between the increased expression of beta-amyloid precursor protein (APP) and the reactive changes in the expression of isoforms of nitric oxide synthase (NOS) in neurons and glial cells after small electrolytic lesions placed to the cerebral cortex. An increase in the expression of APP in both neurons and glial cells was detected 4 days post-operation. The inducible NOS (iNOS) was observed in macrophages or glial cells surrounding the lesion site. No major changes in constitutive NOS (cNOS) were found. APP immunoreactivity was not co-localized with either iNOS or cNOS at this survival time. At longer survival times (8 and 12 days post-lesion), a reactive increase in the expression of cNOS in cortical pyramidal neurons was seen in addition to the elevated expression of iNOS in astrocytes. The reactive expression of cNOS was confined to a subset of neurons also showing a high expression of APP. The present results suggest a relationship between reactive changes in the expression of APP and cNOS during the neuronal response to injury.