Dynorphin immunocytochemical localization in brain and peripheral nervous system: preliminary studies.

Using antisera specific for the opioid peptide dynorphin, we have carried out immunocytochemical studies of the distribution in rat brain and periphery. In the central nervous system, cells that stain positively for dynorphin are found in the supraoptic nucleus, with less-well-stained cells in the paraventricular nucleus of the hypothalamus. Few positive fibers were detected in brain, suggesting problems with fixation and preservation of antigenicity. In pituitary no staining was seen in the anterior and intermediate lobes but heavy staining was detected in the posterior lobe. In the guinea pig, adrenal chromaffin cells stained with dynorphin antisera. Staining of these cells could be blocked with excess of dynorphin-(1-13) or either enkephalin. Radioimmunoassays revealed a great excess of the enkephalins in the adrenal, suggesting cross competition between dynorphin antiserum and adrenal medullary enkephalin. Finally, the dynorphin antiserum stained a complex of fibers in guinea pig ileum. Staining of these fibers could be blocked by moderate amounts of enkephalin as well as by smaller amounts of dynorphin-(1-13). We conclude that in some places (brain and pituitary) dynorphin exists separately from leucine-enkephalin. In other parts of brain and in the periphery the relationship between dynorphin and the enkephalins is very complex and requires further study and improved antisera.