Different Activity Patterns in Retinal Ganglion Cells of TRPM1 and mGluR6 Knockout Mice

Biomed Res Int. 2018 May 8;2018:2963232. doi: 10.1155/2018/2963232. eCollection 2018.


TRPM1, the first member of the melanoma-related transient receptor potential (TRPM) subfamily, is the visual transduction channel downstream of metabotropic glutamate receptor 6 (mGluR6) on retinal ON bipolar cells (BCs). Human TRPM1 mutations are associated with congenital stationary night blindness (CSNB). In both TRPM1 and mGluR6 KO mouse retinas, OFF but not ON BCs respond to light stimulation. Here we report an unexpected difference between TRPM1 knockout (KO) and mGluR6 KO mouse retinas. We used a multielectrode array (MEA) to record spiking in retinal ganglion cells (RGCs). We found spontaneous oscillations in TRPM1 KO retinas, but not in mGluR6 KO retinas. We performed a structural analysis on the synaptic terminals of rod ON BCs. Intriguingly, rod ON BC terminals were significantly smaller in TRPM1 KO retinas than in mGluR6 KO retinas. These data suggest that a deficiency of TRPM1, but not of mGluR6, in rod ON bipolar cells may affect synaptic terminal maturation. We speculate that impaired signaling between rod BCs and AII amacrine cells (ACs) leads to spontaneous oscillations. TRPM1 and mGluR6 are both essential components in the signaling pathway from photoreceptors to ON BC dendrites, yet they differ in their effects on the BC terminal and postsynaptic circuitry.

MeSH terms

  • Amacrine Cells / metabolism
  • Animals
  • Dendrites / metabolism
  • Eye Diseases, Hereditary / metabolism
  • Genetic Diseases, X-Linked / metabolism
  • Mice
  • Mice, Knockout
  • Myopia / metabolism
  • Night Blindness / metabolism
  • Receptors, Metabotropic Glutamate / metabolism*
  • Retina / metabolism*
  • Retinal Bipolar Cells / metabolism
  • Retinal Ganglion Cells / metabolism*
  • Signal Transduction / physiology
  • TRPM Cation Channels / metabolism*


  • Receptors, Metabotropic Glutamate
  • TRPM Cation Channels
  • Trpm1 protein, mouse
  • metabotropic glutamate receptor 6

Supplementary concepts

  • Night blindness, congenital stationary