The spinal antinociceptive effect of nocistatin in neuropathic rats is blocked by D-serine.
BACKGROUND
The neuropeptide nocistatin (NST) has been implicated in the modulation of nociceptive responses in the spinal cord. Depending on the dose, both pronociceptive and antinociceptive effects have repeatedly been reported. The pronociceptive effect is most likely attributable to inhibition of synaptic glycine and gamma-aminobutyric acid release and a subsequent reduction in the activation of inhibitory glycine and gamma-aminobutyric acid receptors, but the mechanisms of its antinociceptive action have hitherto remained elusive. It has recently been demonstrated that synaptically released glycine contributes to N-methyl-D-aspartate receptor activation. The authors therefore investigated whether a reduction in glycine release might also account for the antinociceptive action of NST in neuropathic rats.


METHODS
The authors analyzed the effects of spinally applied NST in the chronic constriction injury model of neuropathic pain. NST was injected intrathecally from nanomolar to picomolar doses and its effects on thermal paw withdrawal latencies were monitored. Furthermore, we tested whether D-serine (100 microg per rat), a full agonist at the glycine binding site of the N-methyl-D-aspartate receptor, would interfere with the effects of NST.


RESULTS
At high doses (10 nmol/rat), intrathecally injected NST was pronociceptive, whereas lower doses (1 pmol/rat) elicited antinociception. The antinociceptive, but not the pronociceptive, action was occluded by intrathecal pretreatment with D-serine. L-serine, which does not bind to N-methyl-D-aspartate receptors, affected neither the pronociceptive nor the antinociceptive effect.


CONCLUSIONS
These results demonstrate that NST produces a biphasic dose-dependent effect on neuropathic pain. The spinal antinociception by NST is most likely attributable to inhibition of glycine-dependent N-methyl-D-aspartate receptor activation.
Muth-Selbach
Uta
U
Klinik für Anaesthesiologie, Universitätsklinikum Düsseldorf, Düsseldorf, Germany. muthslb@uni-duesseldorf.de
Dybek
Eva
E
Kollosche
Katrin
K
Stegmann
Jens-Ulrich
JU
Holthusen
Holger
H
Lipfert
Peter
P
Zeilhofer
Hanns Ulrich
HU
D000701:Analgesics, Opioid / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D000775:Anesthesia, Spinal; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000378:metabolism; D006930:Hyperalgesia / Q000188:drug therapy; D007278:Injections, Spinal; D008026:Ligation; D018847:Opioid Peptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D010146:Pain / Q000188:drug therapy* / Q000209:etiology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D020426:Sciatic Neuropathy / Q000150:complications*; D012694:Serine / Q000494:pharmacology*; D013237:Stereoisomerism
D000701:Analgesics, Opioid; D018847:Opioid Peptides; D016194:Receptors, N-Methyl-D-Aspartate; C111148:nocistatin; D012694:Serine; D005998:Glycine