Histochemical localization of opiate receptors and opioid peptides.

It is possible to localize opiate receptors by histochemical methods. They appear in high densities in anatomical areas associated with physiologic functions altered by opiates. They appear to mediate inhibitory responses; some of them, in certain regions could be involved in axo-axonic synapses. The immunohistochemical studies as well as the electrophysiologic results are compatible with the view that the enkephalins are the endogenous substrates for the opiate receptors.