Nitric oxide, 2-amino-4-phosphonobutyric acid and light/dark adaptation modulate short-wavelength-sensitive synaptic transmission to retinal horizontal cells.
Light-induced changes in the input resistance (Rin) of external, luminosity (i.e. H1) type horizontal cell (HC) perikarya were studied by the bridge-balance method in light-adapted and dark-adapted retinae of carp. Changes in input resistance (delta Rin) induced by short-(460 nm) and long-wavelength (674 nm) flashes, adjusted in intensity to elicit equal-amplitude membrane voltage responses (equal-voltage condition), were measured. In light-adapted retinae, long-wavelength stimuli increased Rin consistently; in contrast, the increase was much less with short-wavelength stimuli. This equal-voltage chromatic delta Rin difference was lost in dark-adapted retinae whereby the delta Rin (an increase) became the same for short- and long-wavelengths. The chromatic delta Rin difference could be recovered by light adaptation or application of sodium nitroprusside to the dark-adapted retinae. Conversely, the equal-voltage chromatic delta Rin difference was eliminated by injection of NG-monomethyl-L-arginine into H1HCs of the light-adapted retinae or by treating the retinae with 2-amino-4-phosphonobutyrate (APB). These results suggest that H1HCs of the carp retina possess distinct postsynaptic mechanisms which mediate short- and long-wavelength signal transmission. Furthermore, it appears that the short-wavelength-sensitive pathway is active only during the light-adapted state of the retina. Taken together, therefore, the short-wavelength transmission to H1HCs probably operates on an APB-sensitive glutamate receptor, with nitric oxide as a light-adaptive messenger.
Furukawa
T
T
Neurosystems Laboratories, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka, Japan.
Yamada
M
M
Petruv
R
R
Djamgoz
M B
MB
Yasui
S
S
D000064:Acclimatization; D000613:Aminobutyrates / Q000494:pharmacology*; D000818:Animals; D002347:Carps; D003624:Darkness; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009569:Nitric Oxide / Q000494:pharmacology / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology*; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000187:drug effects / Q000502:physiology; D012160:Retina / Q000166:cytology / Q000502:physiology*; D019323:omega-N-Methylarginine / Q000494:pharmacology*
D000613:Aminobutyrates; D018690:Excitatory Amino Acid Agonists; D009599:Nitroprusside; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; C012729:2-amino-4-phosphonobutyric acid