Mu2 receptor activation is associated with which effects?

Mu2 receptor activation is associated with which effects?

• A. Analgesia (supraspinal and spinal), miosis, euphoria
• B. Analgesia (spinal ONLY), bradycardia, respiratory depression, constipation, physical dependence
• C. Immune suppression
• D. Analgesia only at supraspinal level

Answer: (B)

Mu opioid receptors have subtypes with distinct effect profiles. Activation of the mu-2 subtype is linked to analgesia confined to the spinal level (spinal analgesia) and the classic opioid adverse effects seen with central and brainstem actions: bradycardia, respiratory depression, constipation, and physical dependence. These effects reflect mu-2’s role in the spinal cord and medullary centers, while supraspinal analgesia, miosis, and euphoria are more closely tied to the mu-1 subtype. Immune suppression is not the defining result of mu-2 activation, and analgesia at the supraspinal level is not a mu-2–mediated effect. So the best description is spinal analgesia with the listed adverse effects, without supraspinal analgesia or mu-1–associated phenomena.

Mu opioid receptors have subtypes with distinct effect profiles. Activation of the mu-2 subtype is linked to analgesia confined to the spinal level (spinal analgesia) and the classic opioid adverse effects seen with central and brainstem actions: bradycardia, respiratory depression, constipation, and physical dependence. These effects reflect mu-2’s role in the spinal cord and medullary centers, while supraspinal analgesia, miosis, and euphoria are more closely tied to the mu-1 subtype. Immune suppression is not the defining result of mu-2 activation, and analgesia at the supraspinal level is not a mu-2–mediated effect. So the best description is spinal analgesia with the listed adverse effects, without supraspinal analgesia or mu-1–associated phenomena.