Amelioration of murine hyperalgesia by intrathecal injection of ketorolac

The amelioration of hyperalgesia by intrathecal injection of ketorolac was studied in mice using focused radiant heat. Hyperalgesia was measured as paw withdrawal latency. Intrathecal injection of ketorolac produced a significant improvement in specific observed behavior interpreted as reduction in hyperalgesia. The intrathecal injection of ketorolac increased the paw withdrawal latency period by forty percent as compared to the control group which received intrathecal injections of 0.9 percent normal saline solution. The maximal suppression of the hyperalgesia occurred two hours after the initial thermal stimulus was applied. Inhibition gradually decreases until the effect disappeared at six hours after stimulus application. This result demonstrated that intrathecal injection of a non-steroidal anti-inflammatory drug (NSAID) prior to a noxious thermal stimulus has an antinociceptive effect. The result supports two hypotheses: First, that NSAIOs exert a spinal as well as peripheral effect. Second, the results provide evidence that prostaglandins have a role in hyperalgesia.