Immunohistochemical localization of kappa opioid receptors in the human frontal cortex

The cellular and subcellular kappa opioid receptor distribution in human frontal cortex was studied using the monoclonal antibody (KA8). kappa opioid receptor-like immunoreactivity was mainly localized in pyramidal neurons of layers II/III and V. In addition, some round and ovoid neurons were found immunolabeled mainly in layer VI. At the ultrastructural level the immunoprecipitate was attached to the cell membrane but was not associated with synaptic specializations. Furthermore, labeling was present in the neuronal perikarya associated with free ribosomes and in the dendrites partly decorating microtubular structures. Previous autoradiographic findings remained restricted to the level of laminar distribution. By contrast, the monoclonal antibody KA8 provides a unique tool to study the cerebral kappa opioid receptor distribution on the cellular and subcellular level.