The combination of NMDA antagonism and morphine produces profound antinociception in the rat dorsal horn.
Dorsal horn nociceptive neurones exhibit wind up, a frequency dependent potentiation of their responses to repeated C-fibre stimulation. Intrathecal morphine (5 micrograms) significantly reduces the initial responses of the neurones but not wind up whereas the reverse is true for N-methyl-D-aspartate (NMDA) antagonists. The combination of intrathecal morphine (5 micrograms) and 7-chlorokynurenate (2.5 micrograms), an antagonist at the glycine site of the NMDA receptor, abolishes both the input and wind up of these neurones.
Chapman
V
V
Department of Pharmacology, University College London, U.K.
Dickenson
A H
AH
D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation; D006358:Hot Temperature; D007278:Injections, Spinal; D007736:Kynurenic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors; D009270:Naloxone / Q000494:pharmacology; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D014110:Touch
D016194:Receptors, N-Methyl-D-Aspartate; D009270:Naloxone; D016202:N-Methylaspartate; D009020:Morphine; D007736:Kynurenic Acid; C057013:7-chlorokynurenic acid