Bidirectional actions of nociceptin/orphanin FQ on A delta-fibre-evoked responses in rat superficial spinal dorsal horn in vitro.
The present study investigated the modulatory actions of nociceptin/orphanin FQ on excitatory glutamatergic transmission in spinal dorsal horn. In transverse spinal cord slices with an attached dorsal root, mono- and polysynaptic A delta-fibre-evoked extracellular field potentials were recorded from superficial dorsal horn. Nociceptin/orphanin FQ showed bidirectional effects on monosynaptic transmission with a potentiation at lower concentrations (100-300 nM) and a dose-dependent depression at higher concentrations (1-3 microM). The polysynaptic field potential was dose-dependently depressed by nociceptin/orphanin FQ (100 nM-3 microM). None of the actions of nociceptin/orphanin FQ was reversed by the non-specific opioid receptor antagonist naloxone, the N-methyl-D-aspartate receptor antagonist D-2-amino-5-phosphonovaleric acid or the peptide nocistatin. The bidirectional actions of nociceptin/orphanin FQ on the monosynaptic field potential may provide an in vitro model for the bidirectional actions of nociceptin/orphanin FQ in behavioural studies showing hyperalgesia at low doses of intrathecal nociceptin/orphanin FQ and analgesia at higher doses.
Ruscheweyh
R
R
Institute of Physiology and Pathophysiology, University of Heidelberg, Im Neuenheimer Feld 326, D-69120 Heidelberg, Germany.
Sandkühler
J
J
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009412:Nerve Fibers / Q000502:physiology*; D018847:Opioid Peptides / Q000494:pharmacology / Q000502:physiology*; D020671:Posterior Horn Cells / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013126:Spinal Nerve Roots / Q000502:physiology; D009435:Synaptic Transmission; D000097629:Nociceptin
D015763:2-Amino-5-phosphonovalerate; D018691:Excitatory Amino Acid Antagonists; D009270:Naloxone; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D000097629:Nociceptin; C111148:nocistatin