Effect of mexiletine on thermal allodynia and hyperalgesia in diabetic mice.

The antinociceptive effect of mexiletine in diabetic mice was examined. Tail-flick latencies at heat intensity of 35 and 50 V in diabetic mice were shorter than those in non-diabetic mice. In diabetic mice, mexiletine increased the tail-flick latency at 35 V to the level observed in non-diabetic mice. The tail-flick latency at 50 V in diabetic mice, but not in non-diabetic mice, was increased by pretreatment with capsaicin (0.56 nmol, i.t., 24 h). The antinociceptive effect of mexiletine in diabetic mice was reduced by capsaicin. These results suggest that the mexiletine-induced antinociception in diabetic mice involves the inhibition of the nociceptive transmission of capsaicin-sensitive primary afferent fibers.