Anatomy of CNS opioid receptors

There is a wide body of evidence to suggest the existence of at least three distinct opioid receptor types in the CNS, referred to as μ, δ, and κ. This paper reviews some of the findings that have led to this conclusion and the anatomical distributions of these sites in the rat brain. Their relation to the opioid peptides and some of the proposed functions mediated by these receptor systems are also discussed.