LM and EM immunolocalization of the gap junctional protein connexin 43 in rat brain.

A site-specific antibody against the principal gap junctional protein in heart (connexin 43) was used to determine immunohistochemically the cellular localization of this protein in rat brain. Structures labelled with the antibody included gap junctional membranes between glial, ependymal, pial and arachnoid cells as well as cytoplasmic membranes and intracellular organelles in close proximity to junctions between these various cell types. No labelling was detected within cell bodies of oligodendrocytes and neurons and no labelled neuronal gap junctions were found. The results suggest that connexin 43 is one of the major gap junctional proteins utilized for junctional coupling between astrocytes and between cells lining the surfaces of the brain.