Effects of blocking non-N-methyl-D-aspartate receptors on visual responses of neurons in the cat visual cortex.
To elucidate the function of non-N-methyl-D-aspartate types of glutamate receptors in the primary visual cortex of the adult cat, we studied the effects of the iontophoretically applied glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione and D-amino-5-phosphonovalerate. Antagonists were applied with ejecting currents that selectively blocked non-N-methyl-D-aspartate receptors. Among 93 cells in which stable recordings were obtained, 6-cyano-7-nitroquinoxaline-2,3-dione reduced the visual response in all cells. The average response magnitude during 6-cyano-7-nitroquinoxaline-2,3-dione administration was reduced to 11.7% of the control (average ejecting current: 41.2 nA). The effect of 6-cyano-7-nitroquinoxaline-2,3-dione was obvious throughout all cortical layers. The effect of D-amino-5-phosphonovalerate on the visual response was tested in 14 cells and it was also effective in blocking the visual response: the average response magnitude during D-amino-5-phosphonovalerate administration was 45.0% of the control (average ejecting current: 41.4 nA). The effect of 6-cyano-7-nitroquinoxaline-2,3-dione on the response was compared in individual cells at both high and low firing rates in order to determine whether a differential effect exists on the level of firing activity of cells due to secondary inactivation of voltage-dependent N-methyl-D-aspartate receptors. However, no indication of response dependency on firing rate was seen with 6-cyano-7-nitroquinoxaline-2,3-dione. We suggest that excitatory transmission at the geniculocortical and corticocortical synapses seems to be strongly dependent on non-N-methyl-D-aspartate receptors throughout the primary visual cortex of the adult cat, and that both non-N-methyl-D-aspartate and N-methyl-D-aspartate type glutamate receptors function additively.
Sato
H
H
Department of Neurophysiology, Osaka University Medical School, Yamadaoka, Suita, Japan. j61343@center.osaka-u.ac.jp
Hata
Y
Y
Tsumoto
T
T
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology*; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010775:Photic Stimulation; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D014793:Visual Cortex / Q000187:drug effects / Q000502:physiology*; D014794:Visual Fields; D014796:Visual Perception / Q000187:drug effects* / Q000502:physiology
D016194:Receptors, N-Methyl-D-Aspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate