Opioid receptor affinities of kappa agonists, agonist/antagonists and antagonists in vitro and in vivo

1. 1. The CMS opioid receptors consist of a major triad: μ, δ and κ.

2. 2. The κ agonists presently available act as κ agonists, δ antagonists and μ₂ isoreceptor antagonists.

3. 3. Pure opiate antagonists possess a broad spectrum of activity at all 3 opioid receptor populations.

4. 4. The Ag/Ant analgesics also possess a broad spectrum of receptor affinities which awaits the definition of complex species differences in their actions.

5. 5. The design of more specific opioid agonists and antagonists will lead to a greater understanding of the many possible roles opioids serve within the CNS.

Author Keywords: opioid receptors; κ; μ; δ; isoreceptors