Mediation of visual responses in the nucleus of the optic tract in cats and rats by excitatory amino acid receptors.

The contribution of excitatory amino acid receptors to visual responses of directional selective neurons in the nucleus of the optic tract (NOT) was examined in anesthetized cats and rats by iontophoretic application of glutamate (GLU), quisqualate (QQL), N-methyl-D-aspartate (NMDA), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 6,7-dinitroquinoxaline-2,3-dione (DNQX) and 2-amino-5-phosphonovalerate (APV). Spontaneous and visually evoked NOT cell activities were increased by GLU, QQL and NMDA. CNQX and DNQX decreased activities predominantly during stimulus movement in the preferred direction, while APV decreased activities to preferred and non-preferred directed stimulus movement. Spontaneous activities were suppressed only following APV application. The results were similar in both species. Furthermore, the effects were similar during binocular stimulation and during monocular stimulation of either eye in the cat. The results indicate a functional role of both non-NMDA and NMDA receptors for the transfer of visual input to directional selective NOT cells in cat and rat.