Antagonism of synaptic potentials in ventral horn neurones by 6-cyano-7-nitroquinoxaline-2,3-dione: a study in the rat spinal cord in vitro.
1. The rat spinal cord in vitro has been used to assess the effect of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) on the dorsal root evoked extracellular ventral root reflex (DR-VRR) and the intracellular excitatory postsynaptic potential (e.p.s.p.) in ventral horn neurones and motoneurones. 2. CNQX (1-5 microM) produces a selective and dose-dependent reduction in the amplitude of the monosynaptic component of the DR-VRR recorded from lumbar spinal segments. 3. With low intensity dorsal root stimulation CNQX selectively attenuates the amplitude of the short latency intracellular e.p.s.p. (70% reduction, P < 0.005) and its rise-time (75%, P < 0.01) without affecting the half-time to decay. 4. When high intensity stimulation is used CNQX significantly attenuates the amplitude of the e.p.s.p. (56%, P < 0.005), rise-time (76%, P < 0.01) and abolishes the short latency spike. In addition longer latency synaptic components are attenuated and the half-time to decay significantly reduced (47%, P < 0.005). 5. The results with CNQX are compared to D-aminophosphonovalerate and discussed in relation to the recruitment of low versus high threshold afferents. The data supports an involvement of non-NMDA receptors in transmission through both mono- and polysynaptic pathways in the ventral horn.
King
A E
AE
Department of Physiology, University of Leeds.
Lopez-Garcia
J A
JA
Cumberbatch
M
M
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006207:Half-Life; D066298:In Vitro Techniques; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D016202:N-Methylaspartate / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology*; D016318:Quisqualic Acid / Q000494:pharmacology; D051381:Rats; D013126:Spinal Nerve Roots / Q000187:drug effects* / Q000502:physiology; D013569:Synapses / Q000187:drug effects* / Q000502:physiology
D011810:Quinoxalines; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D016318:Quisqualic Acid