- 作者: N.J Dun; S.L. Dun; S.Y. Wu; C.A. Williams; E.H. Kwok
- 作者服務機構: Department of Pharmacology and Physiology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, Tenn., USA
- 中文摘要: --
- 英文摘要: Endomorphin (Endo) 1 and 2, two tetrapeptides isolatedfrom the bovine and human brain, have been proposedto be the endogenous ligand for the μ-opiate receptor. Amulti-disciplinary study was undertaken to address theissues of localization, release and biological action ofEndo with respect to the rat dorsal horn. First, immuno-histochemical studies showed that Endo-1- or Endo-2-like immunoreactivity (Endo-1- or Endo-2-L1) is selective-1y expressed in fiber-like elements occupying the superfi-cial layers of the rat dorsal horn, which also exhibit ahigh level of μ-opiate receptor immunoreactivity. Sec-and, release of immunoreactive Endo-2-like substances(irEndo) from the in vitro rat spinal cords upon electricalstimulation of dorsal root afferent fibers was detected bythe immobilized antibody microprobe technique. Thesite of release corresponded to laminae I and II where thehighest density of Endo-2-L1 fibers was localized. Lastly,whole-cell patch clamp recordings from substantia gela-tinosa (SG) neurons of rat lumbar spinal cord slicesrevealed two distinct actions of exogenous Endo-1 andEndo-2: (1) depression of excitatory and/or inhibitorypostsynaptic potentials evoked by stimulation of dorsalroot entry zone, and (2) hyperpolarization of SG neurons.These two effects were prevented by the selective μ-opiate receptor antagonist β-funaltrexamine. The local-ization of endomorphin-positive fibers in superficiallayers of the dorsal horn and the release of irEndo uponstimulation of dorsal root afferents together with theobservation that Endo inhibits the activity of SG neuronsby interacting with μ-opiate receptors provide additionalsupport of a role of Endo as the endogenous ligand forthe μ-opiate receptor in the rat dorsal horn.
- 中文關鍵字: --
- 英文關鍵字: --