Intrathecal [Nphe1]nociceptin( 1-13)NH2 selectively reduces the spinal inhibitory effect of nociceptin

Life Sci. 2002 Jan 25;70(10):1151-7. doi: 10.1016/s0024-3205(01)01496-5.


The effects of intrathecal (i.t.) application of the proposed nociceptin receptor antagonist [Nphe1]nociceptin(1-13)NH2 on the flexor reflex was evaluated in spinalized rats. I.t. [Nphe1]nociceptin (1-13)NH2 dose-dependently facilitated the flexor reflex with no depression. Pretreatment with 16.5 nmol of [Nphe1]nociceptin(1-13)NH2 prevented the development of reflex depression following 0.55 nmol i.t. nociceptin, but strongly enhance the initial excitatory effect of nociceptin. The reflex depressive effect of i.t. endomorphine-2 was not blocked by [Nphe1]nociceptin(1-13)NH2 pretreatment. It is concluded that [Nphe1]nociceptin(1-13)NH2 is a selective antagonist of the spinal receptor mediating the inhibitory action of nociceptin. It can be further suggested that the spinal inhibitory effect of nociceptin may be tonically active.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics / pharmacology*
  • Animals
  • Dose-Response Relationship, Drug
  • Female
  • Injections, Spinal
  • Oligopeptides / pharmacology
  • Opioid Peptides / administration & dosage
  • Opioid Peptides / pharmacology*
  • Peptide Fragments / administration & dosage
  • Peptide Fragments / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Reflex / drug effects
  • Spinal Cord / drug effects*
  • Spinal Cord / physiology


  • Analgesics
  • Oligopeptides
  • Opioid Peptides
  • Peptide Fragments
  • nociceptin-(1-13)-NH2, NPhe(1)-
  • endomorphin 2
  • nociceptin