gms | German Medical Science

102. Jahrestagung der DOG

Deutsche Ophthalmologische Gesellschaft e. V.

23. bis 26.09.2004, Berlin

Two Ni2+-sensitive components of the ERG-b-wave from the isolated bovine retina are related to R- and T-type voltage-gated Ca2+-channels

Meeting Abstract

  • M. Lüke - Institut für Neurophysiologie, Universität zu Köln
  • M. Henry - Institut für Neurophysiologie, Universität zu Köln
  • J. Hescheler - Institut für Neurophysiologie und Zentrum für Molekulare Medizin, Universität zu Köln
  • corresponding author T. Schneider - Institut für Neurophysiologie und Zentrum für Molekulare Medizin, Universität zu Köln
  • W. Sickel - Institut für Neurophysiologie, Universität zu Köln

Evidenzbasierte Medizin - Anspruch und Wirklichkeit. 102. Jahrestagung der Deutschen Ophthalmologischen Gesellschaft. Berlin, 23.-26.09.2004. Düsseldorf, Köln: German Medical Science; 2004. Doc04dogP 163

The electronic version of this article is the complete one and can be found online at:

Published: September 22, 2004

© 2004 Lüke et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.




Neuronal voltage-gated Ca2+ channels trigger transmitter release, secretion, synaptic plasticity, and gene expression. During retinal signal transduction, they regulate the spreading of excitation across the retina. From the ten voltage-gated Ca2+-channels identified so far, those were investigated which cannot be easily blocked pharmacologically as the R- and T-type Ca2+ channels.


Isolated bovine retinae were mounted in a temperature-controlled recording chamber and perfused with an oxygen-saturated standard solution. Electric field potentials were recorded using Ag/AgCl-electrodes, to obtain a complete ERG after each flash of light. After reaching a stable b-wave amplitude, the antagonists were added during a 60 to 75 min long perfusion. Thereupon, the blocker was washed out during 60 - 120 min reperfusion with the standard solution. The changes of a- and b-wave amplitude were calculated and plotted.


NiCl2 (10-100μM) and mibefradil (0.3 - 10μM) do not influence the amplitude of the a-wave. But 100μM NiCl2 blocks the b-wave amplitude completely which is only partially reversible. Ten μM NiCl2 stimulates the b-wave amplitude by 1.3-fold. At lower mibefradil concentrations (0.3 - 1μM), no significant stimulation of b-wave amplitude was observed. The cDNA-fragments of Cav2.3 (R-type) and Cav3.1 (T-type) can be amplified from reverse transcribed total RNA of isolated bovine retina but no transcript of Cav3.2, the most Ni2+-sensitive T-type channel, was detected although we used bovine-specific primer pairs.


The biphasic responses caused by NiCl2 and the inhibition of b-wave by mibefradil reveal to us that besides the well known L-type Ca2+ channels also Ni2+-sensitive Ca2+ channels contribute to the signal transduction in bovine retina, assuming that R-type channels trigger the release of inhibitory and T-type channels trigger the release of excitatory transmitters.