Time-response curve for the intrathecal injection of Phe-Phe amide on the tail-flick latency in non-diabetic (A) and diabetic (B) mice. The nociceptive threshold was determined by the tail-flick test 5, 30 60 and 90 min after injection of the dipeptide. Each point represents the mean with S.E.M. for 10-12 mice. *P < 0.05 and ***P < 0.001 vs. saline-treated group.