A spectral model for signal elements isolated from zebrafish photopic electroretinogram

Vis Neurosci. 2009 Jul-Aug;26(4):349-63. doi: 10.1017/S0952523809990113. Epub 2009 Sep 2.


The zebrafish photopic electroretinogram (ERG) sums isolatable elements. In each element, red-, blue-, green-, and UV- (r, g, b, and u) cone signals combine in a way that reflects retinal organization. ERG responses to monochromatic stimuli of different wavelengths and irradiances were recorded on a white rod suppressing background using superfused eyecups. Onset elements were isolated with glutamatergic blockers and response subtractions. CNQX-blocked ionotropic (AMPA/kainate) glutamate receptors; l-AP4 or CPPG-blocked metabotropic (mGluR6) glutamate receptors; TBOA-blocked glutamate transporters; and l-aspartate inactivated all glutamatergic mechanisms. Seven elements emerged: photopic PIII, the l-aspartate-isolated cone response; b1, a CNQX-sensitive early b-wave element of inner retinal origin; PII, a photopic, CNQX-insensitive composite b-wave element from ON bipolar cells; PIIm, an l-AP4/CPPG-sensitive, CNQX-insensitive, metabotropic subelement of PII; PIInm, an l-AP4/CPPG/CNQX-insensitive nonmetabotropic subelement of PII; a1nm, a TBOA-sensitive, CNQX/l-AP4/CPPG-insensitive, nonmetabotropic, postphotoreceptor a-wave element; and a2, a CNQX-sensitive a-wave element linked to OFF bipolar cells. The first five elements were fit with a spectral model that demonstrates independence of cone-color pathways. From this, Vmax and half-saturation values (k) for the contributing r-, g-, b-, and u-cone signals were calculated. Two signal patterns emerged. For PIII or PIInm, the Vmax order was Vr > Vg >> Vb approximately Vu. For b1, PII, and PIIm, the Vmax order was Vr approximately Vb > Vg > Vu. In either pattern, u-cone amplitude (Vu) was smallest, but u-cone sensitivity (ku362) was greatest, some 10-30 times greater than r cone (kr570). The spectra of b1/PII/PIIm elements peaked near b- and u-cone absorbance maxima regardless of criteria, but the spectra of PIII/PIInm elements shifted from b- toward r-cone absorbance maxima as criterion levels increased. The greatest gains in Vmax relative to PIII occurred for the b- and u-cone signals in the b1/PII/PIIm b-wave elements. This suggests a high-gain prolific metabotropic circuitry for b- and u-cone bipolar cells.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Aspartic Acid / pharmacology
  • Biophysics
  • Color
  • Dose-Response Relationship, Drug
  • Electroretinography / methods
  • Evoked Potentials, Visual / drug effects
  • Evoked Potentials, Visual / physiology*
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Photic Stimulation / methods
  • Principal Component Analysis
  • Retina / cytology*
  • Retinal Bipolar Cells / drug effects
  • Retinal Bipolar Cells / physiology
  • Retinal Bipolar Cells / radiation effects
  • Retinal Cone Photoreceptor Cells / classification
  • Retinal Cone Photoreceptor Cells / drug effects
  • Retinal Cone Photoreceptor Cells / physiology*
  • Retinal Cone Photoreceptor Cells / radiation effects
  • Spectrum Analysis*
  • Visual Pathways / drug effects
  • Visual Pathways / physiology
  • Visual Pathways / radiation effects
  • Zebrafish


  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • benzyloxyaspartate
  • Aspartic Acid