Depressed ventilation and marked constipation are associated with which receptor subtype?

Depressed ventilation and marked constipation are associated with which receptor subtype?

• A. mu, kappa, and delta opioid receptors
• B. mu1 opioid receptors
• C. mu2 opioid receptors
• D. delta opioid receptors

Answer: (C)

Activation of mu opioid receptors has different subtypes with distinct effects. The combination of depressed ventilation and marked constipation is classic for mu2 receptor activation because mu2 receptors are the primary mediators of respiratory depression and decreased gastrointestinal motility. Their presence in brainstem respiratory centers and the enteric nervous system explains why breathing slows and gut motility drops so markedly when these receptors are engaged. Muon1 receptors mainly contribute to supraspinal analgesia and euphoria, with less emphasis on severe respiratory depression and constipation. Delta receptors tend to produce analgesia with a different side-effect profile, and kappa receptors can cause dysphoria and other effects rather than the pronounced respiratory and GI suppression seen with mu2. So the receptor subtype best matching those findings is the mu2 opioid receptor.

Activation of mu opioid receptors has different subtypes with distinct effects. The combination of depressed ventilation and marked constipation is classic for mu2 receptor activation because mu2 receptors are the primary mediators of respiratory depression and decreased gastrointestinal motility. Their presence in brainstem respiratory centers and the enteric nervous system explains why breathing slows and gut motility drops so markedly when these receptors are engaged.

Muon1 receptors mainly contribute to supraspinal analgesia and euphoria, with less emphasis on severe respiratory depression and constipation. Delta receptors tend to produce analgesia with a different side-effect profile, and kappa receptors can cause dysphoria and other effects rather than the pronounced respiratory and GI suppression seen with mu2. So the receptor subtype best matching those findings is the mu2 opioid receptor.