Q. With respect to opioid receptors (Solved)

1. Fentanyl works predominantly at the kappa receptors

2. Both U and delta receptors contribute to respiratory depression

3. Methadone is used for heroin withdrawal because its actions are predominantly at the delta receptors

4. Opioid receptors are coupled to a tyrosine kinase mechanism of action

5. Physical dependence and tolerance is caused by the rapid disintegration of receptors