Excitatory amino acid-mediated components of synaptically evoked input from dorsal roots to deep dorsal horn neurons in the rat spinal cord slice.
The participation of N-methyl-D-aspartate (NMDA) and non-NMDA receptors in the responses of deep dorsal horn neurons to single shock stimulation of dorsal roots was investigated using current- and voltage-clamp techniques. In the presence of Mg2+, superfusion of rat spinal slices with 6-cyano-2,3-dihydroxy-7-nitroquinoxaline (CNQX), a potent antagonist of non-NMDA receptors, reversibly blocks fast excitatory synaptic responses elicited by low-frequency stimulation of dorsal roots and to a greater extent the responses to quisqualate than to kainate or NMDA. The synaptic response elicited in a zero-Mg2+ medium is less sensitive to CNQX. The CNQX-resistant component is however abolished by D-APV, a selective antagonist of NMDA receptor. Under voltage-clamp, the excitatory postsynaptic currents also showed an initial fast (CNQX-sensitive) and a late slow (2-amino-5-phosphonovalerate (APV)-sensitive, Mg2+-sensitive) component, both of which had similar thresholds but differed in their latency, time-to-peak and duration. These results support the concept that both non-NMDA and NMDA receptor channels are present in a majority of deep dorsal horn neurons and could be simultaneously activated by transmitter released from stimulated primary afferents.
Gerber
G
G
Department of Veterinary Physiology and Pharmacology, Iowa State University, Ames 50011.
Randić
M
M
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology*; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000494:pharmacology*; D008274:Magnesium / Q000502:physiology; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000187:drug effects / Q000502:physiology*
D011810:Quinoxalines; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid; D008274:Magnesium