Distribution of neuropeptide FF (FLFQPQRFamide) receptors in the adult rat spinal cord: effects of dorsal rhizotomy and neonatal capsaicin.
By using quantitative autoradiography and highly selective iodinated ligands, we quantified modifications in neuropeptide FF binding sites in the superficial layers (laminae I and II) of the cervical (C6-C8 segments) and lumbar (L3-L5 segments) enlargements in two models: (i) rats neonatally treated with capsaicin; (ii) rat submitted 15 days before to unilateral dorsal rhizotomies. We comparatively analysed the distribution of mu-opioid binding sites in the same animals. We have shown that the [125I]YLFQPQRFamide (neuropeptide FF sites) labelling is not significantly modified following selective damage of fine afferent fibres by neonatal capsaicin treatment. In the cervical and lumbar enlargements, capsaicin-treated/control binding ratios for [125I]YLFQPQRFamide were 0.90 and 0.86, respectively. While unilateral dorsal rhizotomy induced a drastic decrease in [125I]FK-33-824 labelling in the side ipsilateral to the lesion as compared to the intact side of (yielding ratios of 0.29 and 0.31 for cervical and lumbar levels, respectively), [125I]YLFQPQRFamide labelling was not significantly modified, yielding ratios of 0.98 and 0.91 for cervical and lumbar levels, respectively. These data suggest that, in contrast with a majority of mu-opioid receptors, neuropeptide FF receptors are not located on fine primary afferent fibers carrying nociceptive information from the fore- or hindlimb in the rat. This preferential postsynaptic localization, together with the reported "morphine modulating" action of this peptide, support the proposal of a role for neuropeptide FF in intraspinal modulation of nociceptive input.
Lombard
M C
MC
Unité de Recherche de Neurobiologie Pharmacologique, INSERM U.161, Paris, France.
Simonnet
G
G
Zajac
J M
JM
Besson
J M
JM
Allard
M
M
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001345:Autoradiography; D002211:Capsaicin / Q000494:pharmacology*; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009410:Nerve Degeneration / Q000187:drug effects / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D009842:Oligopeptides / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018013:Receptors, Neuropeptide / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000378:metabolism; D019051:Rhizotomy; D013116:Spinal Cord / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D009842:Oligopeptides; D018013:Receptors, Neuropeptide; D017450:Receptors, Opioid, mu; C083929:neuropeptide FF receptor; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; C053651:phenylalanyl-leucyl-phenylalanyl-glutaminyl-prolyl-glutaminyl-arginyl-phenylalaninamide; D002211:Capsaicin