Excitatory amino acid receptors mediate synaptic responses to visual stimuli in superior colliculus neurones of the rat.
Excitatory amino acid receptors are involved in synaptic transmission throughout the central nervous system. As the specific synaptic pharmacology of visually responsive superior colliculus (SC) neurones has not been evaluated, we have attempted to antagonize visual responses of these neurones with selective excitatory amino acid antagonists. The N-methyl-D-aspartate (NMDA) receptor antagonist 3-((+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), and the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were applied iontophoretically in the vicinity of single visually responsive SC neurones. Visually evoked responses were antagonized by non-NMDA receptor selective currents of CNQX in 13 of 14 cells studied. Of 18 cells studied with NMDA receptor selective currents of CPP, visual responses were antagonized in only two cases. This study demonstrates that excitatory amino acid receptors are involved in synaptic transmission of visual information to the rat superior colliculus, but that NMDA receptors may play a relatively minor role.
Department of Visual Science, Institute of Ophthalmology, London, U.K.
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Roberts
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Eaton
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D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000818:Animals; D007051:Ibotenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007478:Iontophoresis; D007608:Kainic Acid / Q000494:pharmacology; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation; D010879:Piperazines; D011810:Quinoxalines; D051381:Rats; D011919:Rats, Inbred Strains; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology; D013477:Superior Colliculi / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
D010879:Piperazines; D011810:Quinoxalines; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D016194:Receptors, N-Methyl-D-Aspartate; D007051:Ibotenic Acid; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid; D007608:Kainic Acid