Blockade of orexin receptor 1 attenuates the development of morphine tolerance and physical dependence in rats

► We injected Orexin receptor 1 antagonist (SB-334867) before morphine injection. ► Repeated injection of SB-334867 decreased the development of morphine tolerance. ► Chronic SB-334867 injection decreased the somatic signs of withdrawal. ► SB-334867 injection before naloxone decreased the somatic signs of withdrawal.