Antinociception induced by acute oral administration of sweet substance in young and adult rodents: The role of endogenous opioid peptides chemical mediators and μ1-opioid receptors

Abstract

The present work aimed to investigate the effects of acute sucrose treatment on the perception of painful stimuli. Specifically, we sought to determine the involvement of the endogenous opioid peptide-mediated system as well as the role of the μ1-opioid receptor in antinociception organisation induced by acute sucrose intake. Nociception was assessed with the tail-flick test in rats (75, 150 and 250g) of different ages acutely pre-treated with 500μL of a sucrose solution (25, 50, 150 and 250g/L) or tap water. Young and Adult rats (250g) showed antinociception after treatment with 50g/L (during 5min) and 150g/L and 250g/L (during 20min) sucrose solutions. Surprisingly, this antinociception was more consistent in mature adult rodents than in pups. To evaluate the role of opioid systems, mature adult rodents were pre-treated with different doses (0.25, 1 or 4mg/kg) of the non-selective opioid receptor antagonist naloxone, the selective μ1-opioid receptor antagonist naloxonazine or vehicle followed by 250g/L sucrose solution treatment. Sucrose-induced antinociception was reduced by pre-treatment with both naloxone and naloxonazine. The present findings suggest that sweet substance-induced hypo-analgesia is augmented by increasing sucrose concentrations in young and adult rodents. Acute oral sucrose treatment inhibits pain in laboratory animal by mediating endogenous opioid peptide and μ1-opioid receptor actions.