Which receptor is the primary mediator of analgesia in most opioid analgesics, and what are the implications of mu receptor activation?

• A. Mu-opioid receptor; activation provides analgesia but also respiratory depression, constipation, miosis, euphoria, sedation, and potential for dependence.
• B. Delta receptor; activation causes sedation only.
• C. Kappa receptor; activation produces analgesia with no side effects.
• D. Gamma receptor; activation causes only respiratory stimulation.

Answer: (A)