TRPV1 and morphine dependence: For example, it has been reported that TRPV1 mRNA increased in the spinal cord and sciatic nerve (2.7 and 3.9 fold, respectively) and decreased in the DRG of morphine-treated rats.10 This finding in conjunction with the results of the present study suggests that change in TRPV1 mRNA level during morphine dependence is target dependent.