Role Central Mu, Delta-1, and Kappa-1 Opioid Receptors in Opioid-induced Muscle Rigidity in the Rat

The present data demonstrate that whereas systemic opiate-induced muscle rigidity is primarily due to the activation of central mu receptors, supraspinal delta(1) and kappa(1) receptors may attenuate this effect. This finding is consistent with previous demonstrations of functional interactions between different central opioid receptor populations in other opiate effects, and could have important pharmacotherapeutic implications.