ABSTRACT
Opiate receptors were first localized autoradiographically in rat brain using in vivo labeling techniques and 3H-diprenorphine. This chapter describes the first detailed maps of a brain receptor and explores much of the groundwork for the in vivo imaging studies using positron emission tomography. Nonetheless, several advantages of in vivo labeling methodology were recognized as investigations were extended from receptor localization to functional aspects of opiate receptors. Correlation of opiate receptor binding with specific pharmacological actions was the next step in establishing the relevancy of these binding sites to the action of opioid compounds. The strongest early evidence for such a correlation was demonstrated by comparing the potency of a series of opiates in inhibiting the electrically induced contraction of the longitudinal muscle of the guinea pig ileum with the affinities derived from in vitro binding assays.
