Involvement of P/Q-type Voltage-dependent Calcium Channels in the Streptozotocin-induced Hyperalgesia in Mice

Streptozotocin-induced diabetic mice displayed a significantly lower mechanical nociceptive threshold than age-matched control mice. In centrast, there was no difference between diabetic mice and control mice in thermal nociceptive threshold. Intrathecal (i. t.) administration of ω-agatoxin IVA (0.33-10 pmol/mouse), a selective blocker of P/Q-type voltage-dependent calcium channels (VDCCs), produced dosedependent inhibition of the mechanical nociceptive response, and its antinociceptive effect at lower doses was greater in diabetic mice than in control mice. The antinociceptive effects of an N-type blocker ω-conotoxin GVIA (0.33-10pmol/mouse, i. t.) and an L-type blocker calciseptine (1-10pmol/mouse, i. t.) were both slightly, but not significantly greater in mice receiving streptozotocin. The antinociception of intrathecal morphine was not different between the experimental groups. Our results indicate that a selective alteration in the role of P/Q-type channels may occur in the spinal processing of mechanic l hypersensitivity in diabetic mice.