Neuropeptide FF and modulation of pain

Neuropeptide FF (NPFF) and the related longer peptide neuropeptide AF (NPAF ) derive from a single gene in several mammalian species. The gene product is expressed mainly in the CNS, where the posterior pituitary and dorsal sp inal cord contain the highest concentrations. Evidence from biochemical and immunohistochemical studies combined with in situ hybridization using NPFF gene-specific probes suggest that all NPFF-like peptides may not derive fr om the characterized NPFF gene, but that other genes can exist which give r ise to related peptides. Intraventricular NPFF exerts antiopioid effects, b ut intrathecal NPFF potentiates the analgesic effects of morphine. NPFF mRN A expression is upregulated in the dorsal horn of the spinal cord after car rageenan-induced inflammation in the hind paw of the rat, but not in the ne uropathic pain model induced by ligation of the spinal roots. NPFF produces a submodality-selective potentiation of the antinociceptive effect induced by brain stem stimulation in the spinal cord during inflammation, and this effect is independent of naloxone-sensitive opioid receptors. In neuropath ic animals, NPFF injected into the periaqueductal grey produces a significa nt attenuation of tactile allodynia, which is not modulated by naloxone. NP FF thus modulates pain sensation and morphine analgesia under normal and pa thological conditions through both spinal and brain mechanisms. (C) 1999 El sevier Science B.V. All rights reserved.