Antinociceptive actions of peripheral glucose administration

The effects of intraperitoneal (ip) d-glucose administration on antinociception were studied in male Long-Evans rats. Rats were assessed for antinociception using the hot-water tail-withdrawal procedure (54 ± 0.2 °C) to determine if peripheral administration of d-glucose (300, 560, or 720 mg/kg) would enhance morphine-mediated antinociception (MMA) (1.0, 3.0, 4.2, 5.6, and 10.0 mg/kg cumulative-dosing regime) and if d-glucose (560, 720, or 1000 mg/kg) alone could produce antinociceptive activity that was naloxone (0.32 mg/kg) reversible. Additionally, the actions of d-glucose on MMA were compared with a stereoisomer, l-glucose, which is not metabolized. The results of these studies demonstrate that peripheral administration of d-glucose significantly enhances MMA and that d-glucose alone produces antinociceptive actions that are potentially mediated by the endogenous opioid system. Furthermore, l-glucose failed to have an effect on MMA suggesting that the alterations in antinociception seen with d-glucose are not due to stressors such as osmolality or injection. The current studies provide evidence that d-glucose alteration of antinociception is not simply a response to taste or gustation.