Functional N-methyl-D-aspartate receptors are expressed in cone-driven horizontal cells in carp retina.
Glutamate works as a major excitatory neurotransmitter in the vertebrate retina. Whole-cell recordings made from isolated carp cone horizontal cells (H1 cells) showed that N-methyl-D-aspartate (NMDA), co-applied with glycine, induced inward currents that were blocked by the NMDA receptor competitive antagonist D-2-amino-5-phosphonopentanoate (D-AP5) and 5,7-dichlorokynurenic acid (DCKA), a selective NMDA receptor antagonist acting at the glycine site on the NMDA receptor complex. Moreover, calcium imaging showed that NMDA caused a significant elevation of intracellular calcium levels ([Ca(2+)](i)) of H1 cells, which was also blocked by D-AP5. In contrast, neither inward currents nor changes in [Ca(2+)](i) could be induced by NMDA in rod horizontal cells (H4 cells). Intracellular recordings made from H1 cells in the isolated retina, superfused with Ringer's containing 1 mM Mg(2+), in the dark demonstrated that NMDA reduced the light-off overshoot of H1 cells. We therefore conclude that the functional NMDA receptor is expressed in carp H1 cells, from which this receptor has been thought to be absent, and this receptor may play a role in modulating cone-driven signal of horizontal cells in the dark.
Shen
Yin
Y
Institute of Neurobiology, Institutes of Brain Science, Fudan University, Shanghai, China.
Zhang
Min
M
Jin
Ying
Y
Yang
Xiong-Li
XL
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D003623:Dark Adaptation / Q000187:drug effects / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D005998:Glycine / Q000494:pharmacology; D006054:Goldfish / Q000033:anatomy & histology / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051248:Retinal Horizontal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014785:Vision, Ocular / Q000187:drug effects / Q000502:physiology
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D002118:Calcium; D005998:Glycine