Morphological and physiological analysis of type-5 and other bipolar cells in the Mouse Retina

Neuroscience. 2016 Feb 19;315:246-58. doi: 10.1016/j.neuroscience.2015.12.016. Epub 2015 Dec 15.

Abstract

Retinal bipolar cells are second-order neurons in the visual system, which initiate multiple image feature-based neural streams. Among more than ten types of bipolar cells, type-5 cells are thought to play a role in motion detection pathways. Multiple subsets of type-5 cells have been reported; however, detailed characteristics of each subset have not yet been elucidated. Here, we found that they exhibit distinct morphological features as well as unique voltage-gated channel expression. We have conducted electrophysiological and immunohistochemical analysis of retinal bipolar cells. We defined type-5 cells by their axon terminal ramification in the inner plexiform layer between the border of ON/OFF sublaminae and the ON choline acetyltransferase (ChAT) band. We found three subsets of type-5 cells: XBCs had the widest axon terminals that stratified at a close approximation of the ON ChAT band as well as exhibiting large voltage-gated Na(+) channel activity, type-5-1 cells had compact terminals and no Na(+) channel activity, and type-5-2 cells contained umbrella-shaped terminals as well as large voltage-gated Na(+) channel activity. Hyperpolarization-activated cyclic nucleotide-gated (HCN) currents were also evoked in all type-5 bipolar cells. We found that XBCs and type-5-2 cells exhibited larger HCN currents than type-5-1 cells. Furthermore, the former two types showed stronger HCN1 expression than the latter. Our previous observations (Ichinose et al., 2014) match the current study: low temporal tuning cells that we named 5S corresponded to 5-1 in this study, while high temporal tuning 5f cells from the previous study corresponded to 5-2 cells. Taken together, we found three subsets of type-5 bipolar cells based on their morphologies and physiological features.

Keywords: ChAT band; HCN1 channel; bipolar cells; patch clamp; voltage-gated Na(+) channel.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / drug effects
  • Axons / physiology
  • Blotting, Western
  • Choline O-Acetyltransferase / metabolism
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / metabolism
  • Immunohistochemistry
  • Male
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Mice, Inbred C57BL
  • Patch-Clamp Techniques
  • Potassium Channels / metabolism
  • Retinal Bipolar Cells / cytology*
  • Retinal Bipolar Cells / drug effects
  • Retinal Bipolar Cells / physiology*
  • Sodium Channel Blockers / pharmacology
  • Sodium Channels / metabolism
  • Tetrodotoxin / pharmacology
  • Tissue Culture Techniques

Substances

  • Hcn1 protein, mouse
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
  • Potassium Channels
  • Sodium Channel Blockers
  • Sodium Channels
  • Tetrodotoxin
  • Choline O-Acetyltransferase