Supraspinal analgesia and prolactin release are produced by which receptor subtype?

Supraspinal analgesia and prolactin release are produced by which receptor subtype?

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

Answer: (B)

Mu1 opioid receptor. Activation of mu1 in brain regions that control pain produces analgesia at the supraspinal level, and it also drives prolactin release by acting on the hypothalamic–pituitary axis (inhibiting dopaminergic tone that normally suppresses prolactin). Mu2 mainly mediates spinal analgesia and is more closely linked to respiratory depression and dependence, while delta and kappa receptors have different profiles. So the combination of supraspinal analgesia and prolactin release is best explained by mu1 receptor activation.

Mu1 opioid receptor. Activation of mu1 in brain regions that control pain produces analgesia at the supraspinal level, and it also drives prolactin release by acting on the hypothalamic–pituitary axis (inhibiting dopaminergic tone that normally suppresses prolactin). Mu2 mainly mediates spinal analgesia and is more closely linked to respiratory depression and dependence, while delta and kappa receptors have different profiles. So the combination of supraspinal analgesia and prolactin release is best explained by mu1 receptor activation.