Effect of ZnCl2 and chelation of zinc ions by N,N-diethyldithiocarbamate (DEDTC) on the ERG b-wave amplitude from the isolated superfused vertebrate retina.
OBJECTIVE
NiCl(2) (15 microM) enhances the ERG b-wave amplitude of vertebrate retina, up to 1.5-fold by blocking E/R-type voltage-gated Ca(2+) channels, which is mediated by blocking the release of GABA onto ionotropic GABA-A and GABA-C receptors. In vivo, it is likely that zinc, rather than nickel ions, may be involved in the modulation of retinal signalling. Therefore, we tested the effect of both, ZnCl(2) (10 to 500 microM) and DEDTC (100 to 500 microM), which chelates zinc ions for the capacity to influence the ERG b-wave amplitude.


METHODS
Transretinal potentials from the isolated bovine retina were recorded as electroretinograms and Ca(2+) inward currents by patch-clamp recordings of stably Ca(v)2.3 transfected HEK-293 cells, yielding an IC(50) value of 5.3 microM for ZnCl(2).


RESULTS
ZnCl(2) (10-15 microM) increased the b-wave amplitude by 1.52-fold +/- 0.12 (n = 6 retinas), which was partially reversible upon washout. The same 1.5-fold stimulation of the b-wave amplitude was reported recently for 15 microM NiCl(2). The superfusion of isolated retinas by DEDTC (100 microM) caused a transient decrease of the ERG b-wave amplitude (0.75-fold +/- 0.06; n = 4), suggesting that the co-secretion of Zn(2+) ions may occur under scotopic conditions.


CONCLUSIONS
The stimulatory effect of ZnCl(2) on the ERG b-wave amplitude resembles the stimulatory effect of NiCl(2) and may be mediated rather by the NiCl(2)-sensitive, Ca(v)2.3 E-/R-type voltage-gated Ca(2+) channels than by NiCl(2)-sensitive T-type channels.
Siapich
Siarhei A
SA
Institute of Neurophysiology, University of Cologne, Köln, Germany.
Wrubel
Heiko
H
Albanna
Walid
W
Alnawaiseh
Maged
M
Hescheler
J
J
Weiergräber
Marco
M
Lüke
Matthias
M
Schneider
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type; D020908:Calcium Channels, R-Type / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology*; D002712:Chlorides / Q000494:pharmacology*; D004050:Ditiocarb / Q000031:analogs & derivatives* / Q000494:pharmacology; D004596:Electroretinography / Q000187:drug effects*; D006801:Humans; D007668:Kidney / Q000196:embryology / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D017967:Zinc Compounds / Q000494:pharmacology*
C423009:CACNA1E protein, human; C529218:CACNA1S protein, mouse; D020746:Calcium Channels, L-Type; D020908:Calcium Channels, R-Type; D027682:Cation Transport Proteins; D002614:Chelating Agents; D002712:Chlorides; D017967:Zinc Compounds; C016837:zinc chloride; D004050:Ditiocarb; C039353:dihydroxyethyldithiocarbamate; D002118:Calcium