Figure 6. Effect of 8 nmol DAMGO on muscle tone. Two intracerebroventricular injections were performed: one at time 0 and one at 10 min. Experimental group Sal/DAMGO (n = 9) received first saline and then DAMGO; the CTAP/DAMGO group first received 3 nmol CTAP and then DAMGO (n = 10). The administration of DAMGO significantly increased the muscle tone ((section)P < 0.001) compared with the baseline values. This effect was attenuated by pretreatment with CTAP (P < 0.05 for all time points). The electromyographic activity at some time points (indicated by *) within CTAP/DAMGO group was no different from the baseline values.