Which opioid receptor is primarily associated with mediating euphoria and pruritus?

The opioid receptor primarily associated with mediating euphoria and pruritus is the Mu-1 receptor. This receptor subtype, part of the mu receptor family, is linked to the pleasurable effects of opioids, such as pain relief and feelings of euphoria, which enhance the overall experience of well-being. Activation of the Mu-1 receptor can also lead to the sensation of itchiness or pruritus, a side effect often noted with opioid use.

In contrast, other receptor subtypes have different primary functions. The kappa receptor is more associated with dysphoria and can also lead to sedation without the same euphoric effects. The delta receptor is involved in modulating the emotional response to pain and may function in a more complex manner regarding mood. Lastly, the Mu-2 receptor is more related to the respiratory depression and physical dependence that can occur with opioid use, rather than euphoria or pruritus. Thus, the distinctive qualities of the Mu-1 receptor reinforce its role in these sensations.