A psychiatric-mental health nurse practitioner is employed at an inpatient substance abuse facility. A new patient is a 33-year-old man who recently overdosed on fentanyl and had to be resuscitated with naloxone. Activation of which opioid receptor triggers respiratory depression?

Choice A reason: The mu-opioid receptor is primarily responsible for the analgesic and euphoric effects of opioids, but it also mediates respiratory depression. Fentanyl, a potent mu-opioid receptor agonist, can cause life-threatening respiratory suppression, which is reversed by naloxone, a mu-opioid antagonist. Choice B reason: The kappa-opioid receptor is involved in analgesia and dysphoria but does not significantly contribute to respiratory depression. Its activation may produce sedation but not the profound respiratory effects seen with mu receptor activation. Choice C reason: The delta-opioid receptor plays a role in modulating mood and analgesia but is not primarily associated with respiratory depression. Its effects are less potent and less clinically relevant in overdose scenarios. Choice D reason: Omega is not a recognized opioid receptor subtype. It is not involved in opioid pharmacodynamics and is not relevant to respiratory depression.