Autoradiographic localisation of opiate receptors in rat small intestine.

[3H]Naloxone and [3H]dihydromorphine are selective ligands for opiate receptors. Using an in vitro autoradiographic technique, binding of these ligands has been demonstrated to the villi and crypts in rat small intestine. These results indicate the presence of opiate receptor sites in the small intestine which suggests further a role for endogenous opiates in the transport functions of intestinal mucosa.