Differential distribution of a neurofilament protein epitope in acetylcholinesterase-rich neurons of human cerebral neocortex

The majority of acetylcholinesterase-rich pyramidal neurons in neocortical layers III and V of the human brain displayed intense immunostaining with SMI-32, a monoclonal antibody which recognizes a non-phosphorylated epitope of neurofilament proteins. In contrast, very few of the heteromorphic acetylcholinesterase-rich perikarya embedded in the white matter of the cerebral hemispheres are associated with this type of immunostaining. These two groups of acetylcholinesterase-rich cortical neurons can thus be differentiated not only on the basis of morphology and location but also on the basis of cytochemical signature. The concurrent visualization of SMI-32 immunoreactivity and acetylcholinesterase enzyme activity also showed that SMI-32 immunoreactive neurons can be subdivided into several subgroups on the basis of their perikaryal acetylcholinesterase activity.