The central versus peripheral antinociceptive effects of μ-opioid receptor agonists in the new model of rat visceral pain

► DAMGO and morphine were analgesics in the rat model of late permanent visceral pain. ► DAMGO was equipotent with morphine by i.p. and more potent by i.c.v. administration. ► To demonstrate the site of action of drugs, a quaternary opioid antagonist was used. ► The effect of i.p. DAMGO is predominantly mediated by peripheral opioid receptors. ► The effect of i.p. morphine is mediated by central and peripheral opioid receptors.