Figure 6. Effects of i.c. microinjection with β-FNA, naltrindole or nor-BNI into the contralateral thalamic VM nucleus on bilateral mechanical- and heat-evoked paw withdrawal reflexes during the condition of 30 min 43°C i.m. single heating-needle stimulation.

Bilateral heat hypoalgesia induced by ipsilateral i.m. 43°C heating-needle stimulation were significantly depressed by i.c. microinjection with δ-opioid antagonist naltrindole, but not the other opioid receptor antagonists, into the contralateral thalamic VM nucleus. *P < 0.05 compared with the 43°C i.m. single heating-needle stimulation group. #P < 0.05 compared with the vehicle (0.9% saline) treatment group. BO, baseline response before the i.c. catheterization; B, baseline response before the i.m. heating-needle stimulation; p, post i.c. injection. n = 8 for each group.