Novel proteoglycan epitope expressed in functionally discrete patterns in primate cortical and subcortical regions.

The molecular diversity of neuronal subpopulations was examined with a new monoclonal antibody, 8B3, that recognizes a condroitin sulfate proteoglycan expressed in anatomically discrete domains of central nervous system regions. In the neocortex, interneurons display 8B3 immunoreactivity in a rostrocaudal gradient, with a distinctive staining pattern that distinguishes known cytoarchitectonic and functional boundaries. The distribution pattern of 8B3 immunoreactivity in subcortical structures is very restricted. In the striatum, 8B3 stains spiny stellate neurons clearly defining a compartment that may correspond to the matrix. Gradients of immunoreactivity are detected in the putamen, globus pallidus, and deep cerebellar nuclei, where the most dense areas of 8B3 immunoreactivity corresponds to zones of polysynaptic projections to association prefrontal cortex. In contrast, the sensorimotor domains express lower levels of immunoreactivity. Only the projection neurons of the ventrolateral nucleus and the GABAergic neurons of the reticular nucleus express significant 8B3 immunoreactivity in the thalamus. In the spinal cord, 8B3 immunoreactivity is primarily associated with a subpopulation of motor neurons in the ventral horn and neurons in Clarke's nucleus. The complex distribution pattern reflects novel aspects of the functional organization of cortical and subcortical systems in the CNS of the primate brain and represents a potentially useful tool to assess subpopulations of neurons and brain areas as putative targets in human disease.