Muscle rigidity due to opioids is because of their effect on?

Ans. is 'a' i.e., mu o Opioids appear to produce their physiologic effects by binding to at least three types of opioid receptors, the mu GO, delta (b), and Kappa (K). Muscle rigidity occurs after administration of supra-analgesic doses of potent mu preferring agnoists like a fentaniL "The present data demonstrate that opiate-induced muscle rigidity is primarily due to the activation of central mu receptors, and supraspinal delta and kappa receptors may attenuate this effect"