Antinociceptive effect of chronic administration of green tea epigallocatechin gallate in a model of diabetic hyperalgesia in rat

Considering antidiabetic and antiinflammatory potential of geen tea epigallocatechin-gallate (EGCG), this study was designed to investigate the analgesic effect of two-month EGCG using formalin and tail-immersion tests in diabetic rats. Male rats were divided into control, EGCG -treated control, diabetic, EGCG -treated diabetic, and sodium salicylate-treated control and diabetics. EGCG was administered p.o. at doses of 20 and 40mg/kg for seven weeks one week after diabetes induction. At the end of the study, pain threshold and nociception were evaluated using hot water tail immersion and formalin tests respectively. Diabetic rats exhibited a higher score of pain at both phases of the formalin test and EGCG-treated diabetic rats dose-dependently exhibited a lower nociceptive score at both phases of the test (p<0.05). Regarding pain threshold, diabetes significantly reduced tail immersion latency (p<0.05) and EGCG treatment did not produce a significant change in this respect. Although chronic treatment with EGCG does not affect pain threshold but significantly reduces nociception in an experimental model of hyperalgesia and this may be considered as an auxiliary treatment for diabetic hyperalgesia.

Keywords: Epigallocatechin-3-gallate, Pain, Hyperalgesia, Diabetic rat