Neuropeptide FF in the rat spinal cord during carrageenan inflammation

The role of neuropeptide FF (NPFF) in the modulation of spinal nociception was studied in rats with carrageenan inflammation in the hind paw. Normally no NPFF-ir neuronal cell bodies are found in the spinal cord. During inflammation NPFF-neurons were seen in an area receiving innervation from the inflamed hind limb, but in rats pretreated with morphine no NPFF-ir neurons were found. NPFF or IgG from NPFF immunoserum administered intrathecally had no effect in thermal and mechanical nociceptive tests. Morphine produced significant antinociception in both tests in the inflamed paw, but the effect was not modified by NPFF. These findings differ from the effects of intrathecal administration of NPFF and opioids in acute thermal tests when no inflammation is present. The role of NPFF in the modulation of nociception in the spinal cord may be markedly changed during acute inflammation.