Receptor Subtypes in Opioid and Stimulant Reward

Abstract: Studies of the behaviourally‐reinforcing actions of opioid and stimulant drugs of abuse are reviewed in an attempt to identify their reward‐related brain receptors. We focus on data generated by drug self‐administration, brain stimulation reinforcement, and conditioned place preference paradigms. A consistent body of evidence supports a role for μ and δ, but not K, receptors in opioid reward. Stimulant reward apparently involves both D₁ and D₂ receptors; the data favour D₂ mediation of stimulant drug reinforcement with a permissive or modulatory role for D₁ receptors. The reward‐relevant opioid and dopamine receptors, as well as the cannabinoid (marijuana) receptor, share the ability to couple G_i proteins that mediate inhibition of adenylate cyclase and stimulation of K⁺ conductance. These signal transduction mechanisms thus may be generally implicated in the reinforcing properties of diverse drugs of abuse. 1992 Nordic Pharmacological Society