Visualization of opiate receptors and opioid peptides in sequential brain sections

Autoradiographic and immunocytochemical studies were carried out on adjacent sections from formaldehyde-perfused rat brains in order to directly correlate the distribution of opiate receptors and opioid peptides. Perfusion fixation of the brains resulted in a partial loss of specific [3H]naloxone binding with essentially no change in the pharmacological properties of the remaining sites. When the distribution of sites was compared to that of enkephalin immunoreactivity in adjacent sections, striking correlations were observed in a number of areas throughout the neuraxis. Adjacent section autoradiography-immunocytochemistry should provide a useful tool for relating the anatomical distribution of opiate receptor subtypes to different opioid peptide neuronal systems.