Cannabinoid CB1 receptor upregulation in a rat model of chronic neuropathic pain

Abstract Although cannabinoids are known to be more effective analgesics against chronic rather than acute pain, the mechanism underlying this phenomenon is still unclear. We report now that contralateral thalamic cannabinoid CB 1 receptors are upregulated after unilateral axotomy of the tibial branch of the sciatic nerve, a rat model of chronic neuropathic pain, and hypothesize that cannabinoid CB 1 receptor upregulation contributes to the increased analgesic efficacy of cannabinoids in chronic pain conditions.