With respect to opioid receptors

• A. Fentanyl works predominantly at the kappa receptors
• B. Both U and delta receptors contribute to respiratory depression
• C. Methadone is used for heroin withdrawal because its actions are predominantly at the delta receptors
• D. Opioid receptors are coupled to a tyrosine kinase mechanism of action
• E. Physical dependence and tolerance is caused by the rapid disintegration of receptors