Comparison of [125I]-bolton-hunter substance P binding in young and aged rat spinal cord.
Binding of [125I]-labeled Bolton-Hunter substance P ([125I]-BHSP) to NK1 receptors was investigated in the spinal cord of young (3-4 month) and aged (14-16 month) rats. In homogenates of whole spinal cord, the affinity (equilibrium dissociation constant, approximately 210 pM) and maximum density of [125I]-BHSP binding sites ( approximately 0.25 fmol/mg wet weight) were similar for young and aged rats. Autoradiographic studies revealed a similar distribution of [125I]-BHSP sites in both young and old rats at all spinal levels. Intense binding was observed in the superficial dorsal horn (laminae I-III), grey commissure (lamina X) and thoracic intermediolateral cell column (IML) with lower levels of binding in the deeper dorsal horn (laminae IV-VI) and ventral horn (laminae VII-IX). However, the density of [125I]-BHSP sites was significantly (P<0.05) lower in lamina X of lumbar sections of aged rats compared with young controls. These studies suggest that ageing is associated with a selective loss of NK1 receptors in lamina X of the lumbar spinal cord, although the affinity of NK1 receptors in aged rats is unchanged.
Maguire
C M
CM
Department of Biomedical Science, University of Tasmania at Launceston, P.O. Box 1214, Launceston, Tasmania 7250, Australia.
Geraghty
D P
DP
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites / Q000502:physiology; D007457:Iodine Radioisotopes; D008161:Lumbosacral Region; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D013116:Spinal Cord / Q000254:growth & development / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*; D013388:Succinimides / Q000378:metabolism*
C043194:Bolton Hunter reagent-substance P conjugate; D007457:Iodine Radioisotopes; D018040:Receptors, Neurokinin-1; D013388:Succinimides; D013373:Substance P