Figure 4.
Effect of repeated injection of fentanyl on the fentanyl-induced increase in [35S] GTPgS binding to membranes of the ipsilateral side of the spinal cord obtained from sham-operated and sciatic nerve-ligated β-endorphin knockout (KO) mice. Repeated s.c. injection of fentanyl was started 7 days after sciatic nerve ligation. Mice were repeatedly injected fentanyl once a day for 14 consecutive days. During the first 6 days after surgery, mice were not treated with fentanyl. Membranes were prepared at 21 days after nerve ligation. Each value represents the mean ± standard error of the mean of six samples. Each group was consisted of four males and two females. n.s. = not significant