Antinociceptive properties of intrathecal dexmedetomidine in rats

Dexmedetomidine is a highly selective α₂-adrenoceptor agonist. In this study, the intrathecal administration of dexmedetomidine into the rat lumbar subarachnoid space produced dose-dependent, prolonged antinociception as measured by hot plate and tail flick testing. Intrathecal administration of 3 or 10 μg of dexmedetomidine increased hot plate and tail flick latencies to cutoff values within 15 min of injection. Animals receiving 1 μg of intrathecal dexmedetomidine did not show any significant antinociception when compared to saline controls. The intrathecal administration of the α₂-adrenoceptor antagonist, idazoxan, ablated all measurable antinociception produced by the prior injection of 10 μg of dexmedetomidine.