Genetic targeting and physiological features of VGLUT3+ amacrine cells

Vis Neurosci. 2011 Sep;28(5):381-92. doi: 10.1017/S0952523811000290. Epub 2011 Aug 25.

Abstract

Amacrine cells constitute a diverse class of interneurons that contribute to visual signal processing in the inner retina, but surprisingly, little is known about the physiology of most amacrine cell subtypes. Here, we have taken advantage of the sparse expression of vesicular glutamate transporter 3 (VGLUT3) in the mammalian retina to target the expression of yellow fluorescent protein (YFP) to a unique population of amacrine cells using a new transgenic mouse line. Electrophysiological recordings made from YFP-positive (VGLUT3+) amacrine cells provide the first functional data regarding the active membrane properties and synaptic connections of this recently identified cell type. We found that VGLUT3+ amacrine cells receive direct synaptic input from bipolar cells via both N-methyl-d-aspartate receptors (NMDARs) and non-NMDARs. Voltage-gated sodium channels amplified these excitatory inputs but repetitive spiking was never observed. VGLUT3+ amacrine cells responded transiently to both light increments (ON response) and decrements (OFF response); ON responses consisted exclusively of inhibitory inputs, while OFF responses comprised both excitatory and inhibitory components, although the inhibitory conductance was larger in amplitude and longer in time course. The physiological properties and anatomical features of the VGLUT3+ amacrine cells suggest that this bistratified interneuron may play a role in disinhibitory signaling and/or crossover inhibition between parallel pathways in the retina.

Publication types

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

MeSH terms

  • Amacrine Cells / classification
  • Amacrine Cells / drug effects
  • Amacrine Cells / physiology*
  • Amino Acid Transport Systems, Acidic / genetics
  • Amino Acid Transport Systems, Acidic / metabolism*
  • Animals
  • Animals, Newborn
  • Biophysics
  • Cadmium Chloride / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / genetics
  • Green Fluorescent Proteins / genetics
  • In Vitro Techniques
  • Light
  • Membrane Potentials / drug effects
  • Membrane Potentials / genetics*
  • Mice
  • Mice, Transgenic
  • Peptides / pharmacology
  • Retina / cytology*
  • Retinal Bipolar Cells / drug effects
  • Retinal Bipolar Cells / physiology
  • Sodium Channel Blockers / pharmacology
  • Synapses / genetics
  • Synapses / physiology
  • Tetrodotoxin / pharmacology
  • Whole Blood Coagulation Time

Substances

  • Amino Acid Transport Systems, Acidic
  • Excitatory Amino Acid Antagonists
  • Peptides
  • Sodium Channel Blockers
  • vesicular glutamate transporter 3, mouse
  • Green Fluorescent Proteins
  • Tetrodotoxin
  • iberiotoxin
  • Cadmium Chloride