Intrathecal neuropeptide Y inhibits behavioral and cardiovascular responses to noxious inflammatory stimuli in awake rats

To test the hypothesis that administration of neuropeptide Y (NPY) to the spinal cord reduces inflammatory pain, we evaluated the effects of intrathecal NPY on behavioral and cardiovascular markers of the nociception associated with intraplantar formalin injection in rats. Before the administration of formalin, NPY dose dependently increased blood pressure, an effect that could be prevented with the coadministration of the Y2 antagonist, BIIE0246. This effect lasted only 20 min, and thus was over before initiation of the formalin test. NPY dose dependently inhibited the flinching, licking, pressor, and tachycardia responses associated with formalin injection. The Y1 receptor antagonist BIBO 3304 partially reversed the antinociceptive effect of NPY at a dose that did not by itself have an effect (3 μg). We conclude that intrathecal NPY acts in part via Y1 receptors to inhibit ongoing inflammatory nociception.