Thalamic NMDA receptors and nociceptive sensory synaptic transmission.
The responses of single thalamic neurones to noxious thermal stimulation were recorded in anaesthetized rats. The selective N-methyl-D-aspartate (NMDA) receptor antagonist, 3-((+-)-2-carboxypiperazin-4-yl)propyl-l-phosphonate (CPP), antagonised nociceptive responses when ejected iontophoretically with currents which produced selective antagonism at NMDA receptors. In contrast, the non-NMDA excitatory amino acid receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNOX) had little or no effect on nociceptive responses, although it was able to reduce responses to non-nociceptive mechanoreceptor input. These results show that there is substantial NMDA receptor involvement in thalamic nociceptive responses, and that the contribution of CNQX-sensitive non-NMDA receptors to these responses is not extensive. Furthermore, it appears that nociceptive and non-nociceptive input to the thalamus have distinct synaptic pharmacologies.
Eaton
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Department of Visual Science, Institute of Ophthalmology, London, U.K.
Salt
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D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D006358:Hot Temperature; D008297:Male; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D010879:Piperazines / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D013788:Thalamus / Q000187:drug effects / Q000502:physiology*
D010879:Piperazines; D011810:Quinoxalines; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid