2-Deoxy-D-glucose-induced decrements in operant and reflex pain thresholds

Acute exposure to many environmental stressors induces significant analgesia. The present study examined whether 2-deoxy-D-glucose (2-DG), an antimetabolic glucose analogue, which induces glucoprivation and peripheral sympatho-adrenal discharge, would also produce analgesia as measured by either an operant liminal escape or a reflex tail-pinch procedure. In the liminal escape paradigm, 9 rats were tested at weekly intervals in 6 randomly selected testing conditions: 30 min pre-test injections of four 2-DG doses (100, 225, 350 and 700 mg/kg, IP) and 180 min pre-test injections of the 2 higher doses. Moderate analgesia occurred at the lower 2-DG doses 30 min after injection, while profound analgesia occurred at the higher doses. After 180 min, only the 700 mg/kg 2-DG dose produced moderate analgesia, which was further enhanced by food deprivation. Rats tested in the tail-pinch paradigm displayed a similar dose-dependent analgesia course. These results demonstrate that 2-DG decreases nociceptive sensitivity, possibly through stress-induced activation of an intrinsic pain-inhibitory system.