Activation of peripheral delta-opioid receptors leads to anti-hyperalgesic responses in the masseter muscle of male and female rats

▶Peripheral δ opioid receptors (DORs) mediate anti-hyperalgesic responses under acute myositis. ▶Peripheral DORs produce more potent responses in male than female rats. ▶There are no sex differences in the basal level of DOR expression in TG. ▶The effect of peripheral DORs is mediated via ATP-dependent K+ channels.