Hemichannel-mediated inhibition in the outer retina

Science

Volumn 292, Issue 5519, 2001, Pages 1178-1180

  Kamermans, Maarten ^a   Fahrenfort, Iris ^a   Schultz, Konrad ^b   Janssen Bienhold, Ulrike ^b   Sjoerdsma, Trijntje ^a   Weiler, Reto ^b  

^a NETHERLANDS INSTITUTE FOR NEUROSCIENCE   (Netherlands)

^b UNIVERSITY OF OLDENBURG   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

CELLS; FEEDBACK; NEUROLOGY; VISION;

HEMICHANNELS;

BIOMEDICAL ENGINEERING;

CALCIUM CHANNEL;

ARTICLE; CALCIUM CURRENT; DENDRITE; FEEDBACK SYSTEM; HYPERPOLARIZATION; NEGATIVE FEEDBACK; POLARIZATION; PRIORITY JOURNAL; RETINA; RETINA CONE; SYNAPSE;

ANIMALS; CALCIUM; CALCIUM CHANNELS; CARBENOXOLONE; CARPS; CONES (RETINA); CONNEXINS; DENDRITES; ELECTRIC CONDUCTIVITY; EXCITATORY AMINO ACID AGONISTS; FEEDBACK; GLUTAMIC ACID; IMMUNOHISTOCHEMISTRY; ION CHANNEL GATING; KAINIC ACID; LIGHT; MEMBRANE POTENTIALS; MODELS, NEUROLOGICAL; RETINA; SYNAPSES;

EID: 0035844021     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1060101     Document Type: Article

References (26)

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7. At present, there is no specific blocker for Cx26 hemichannels. Carbenoxolone has blocked other gap junctions in the retina. This has not influenced our results because full-field light stimuli were used in eliminating lateral communication between HCs via gap junctions.
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10. Retinas of light-adapted goldfish, Carassius auratus, (12-to 16-cm standard body length) were used in the electrophysiological experiments. For details about the experimental procedures, see I. Fahrenfort, R. L. Habets, H. Spekreijse, and M. Kamermans [J. Gen. Physiol. 114, 511 (1999)]. All experiments were done in the presence of 25 μM SKF 89976, a kind gift from Smith Kline Beecham, to block the influence of the CABAergic system in the outer retina without affecting the inner retina. Data are presented as mean ± SEM.
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16. 2+ current of about 9 mV. In conditions where feedback is not active, such a shift reduces synaptic transmission between cones and HCs by about 90% (15). This accounts for the large hyperpolarization of the HCs and the reduction of the HC light responses.
17. In the dark, the resting potential of HCs is -34.7 ± 3.6 mV (n = 12). Blocking the glutamate-gated conductances with DNQX (an antagonist of ionotropic, non-NMDA glutamate receptors) in the control condition induced a hyperpolarization of -36.7 mV ± 2.8 mV (n = 7) in HCs which is significantly less than the carbenoxolone-induced hyperpolarization (-44.4 = 3.0 mV) (t test, P < 0.05). Application of DNQX during carbenoxolone further hyperpolarized HCs by -3.6 ± 1.3 mV (n = 5), to a final value of -82.7 mV. Taking this as the reversal potential for the potassium conductance and 0 mV as the reversal potential for the cation and hemichannel conductances, one can estimate, using Ohms law, that the hemichannel conductance is about one-eighth of the cation conductance.
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19. Web figure 1 is available at Science Online at www. sciencemag.org/cgi/content/full/292/5519/1178/ DC1.
20. 2+ current by 10 mV. Because in goldfish cones 5 to 16 synaptic ribbons are present with each at least two HC dendrites per ribbon [W. K. Stell, R. Kretz, D. O. Lightfoot, in The S-potential, B. J. Drujan and M. Laufer, Eds. (Liss, New York, 1982), pp. 51-75], one would need about 13 to 400 hemichannels per dendrite.
21. 2+ current by 10 mV. Because in goldfish cones 5 to 16 synaptic ribbons are present with each at least two HC dendrites per ribbon [W. K. Stell, R. Kretz, D. O. Lightfoot, in The S-potential, B. J. Drujan and M. Laufer, Eds. (Liss, New York, 1982), pp. 51-75], one would need about 13 to 400 hemichannels per dendrite.
22. 2+ current by 10 mV. Because in goldfish cones 5 to 16 synaptic ribbons are present with each at least two HC dendrites per ribbon [W. K. Stell, R. Kretz, D. O. Lightfoot, in The S-potential, B. J. Drujan and M. Laufer, Eds. (Liss, New York, 1982), pp. 51-75], one would need about 13 to 400 hemichannels per dendrite.
23. 2+ current by 10 mV. Because in goldfish cones 5 to 16 synaptic ribbons are present with each at least two HC dendrites per ribbon [W. K. Stell, R. Kretz, D. O. Lightfoot, in The S-potential, B. J. Drujan and M. Laufer, Eds. (Liss, New York, 1982), pp. 51-75], one would need about 13 to 400 hemichannels per dendrite.
24. J. Klooster, K.M. Studholme, S. Yazulla. Invest. Ophthalmol. Vis. Sci (Suppl). 42(4), S727 (2001).
25. K. Schultz, U. Janssen-Bienhold, R. Weiler, J. Comp. Neurol., in press.
26. This work was supported by the Netherlands Organization for Scientific Research (NWO), the Deutsche Forschungsgemeinschaft (SFB 517) and the German Israeli Foundation. We would like to thank J. S. McReynolds, P. S. Sterling, H. Spekreijse, and S. Yazulla for their critical reading of the manuscript.