Targeted expression of μ-opioid receptors in a subset of striatal direct-pathway neurons restores opiate reward

μ-opioid receptor (MOR) was previously shown to be necessary for opiate reward, analgesia and dependence. To better understand the specific anatomical and cell type loci of MOR action in opiate reward and reinforcement learning, the authors use cell-specific rescue expression of MOR in subtypes of neurons in the mouse brain that lack MOR globally and show that MOR in the striatal direct-pathway medium spiny neurons is sufficient to rescue the reward action of opioids without affecting opioid analgesia or withdrawal in MOR knockout mice.