Summary: New research shows that losing a single ion channel, TRPM1, is sufficient to trigger persistent rhythmic electrical oscillations in the retina. These pathological oscillations appear in conditions such as congenital stationary night blindness (CSNB) and retinitis pigmentosa (RP). By comparing Trpm1 and mGluR6 knockout mice, the study identifies a destabilized circuit between rod bipolar cells and AII amacrine cells that produces anti‑phase oscillations that interfere with normal visual signaling.
Structural remodeling of bipolar cell axon terminals and a hyperpolarized resting state of bipolar cells further destabilize retinal circuitry, generating spontaneous neural noise that distorts perception. The results emphasize that restoring vision after photoreceptor injury or loss will likely require therapies that both replace lost photoreceptor input and suppress or stabilize oscillatory activity in inner retinal circuits.
Key Facts
- TRPM1 loss drives oscillations: Removing the TRPM1 ion channel disrupts ON‑bipolar cell signaling and produces pathological retinal oscillations.
- Circuit instability identified: Weakened coupling between rod bipolar cells and AII amacrine cells and anti‑phase signaling across ON and OFF pathways create rhythmic neural noise.
- Therapeutic implication: Effective vision restoration should address oscillatory activity in addition to restoring photoreceptor signals to avoid distorted or hallucinatory perception.
Source: Ritsumeikan University
Overview
Pathological rhythmic activity in the retina—commonly called retinal oscillations—has been documented in several eye diseases, including congenital stationary night blindness (CSNB) and retinitis pigmentosa (RP). These spontaneous oscillations disrupt the normal flow of visual information from the eye to the brain, often degrading or distorting perception. While oscillatory behavior of retinal ganglion cells (RGCs) has been reported for years, the specific cellular and circuit mechanisms responsible have been unclear.
A recent study led by Sho Horie, a PhD candidate in the Graduate School of Pharmacy at Ritsumeikan University, with Professors Katsunori Kitano, Masao Tachibana, and Chieko Koike, identified a mechanism linking TRPM1 channel deficiency to persistent retinal oscillations. The study was published online in The Journal of General Physiology on October 16, 2025.
What the researchers did
TRPM1 is a cation channel located in the dendrites of ON bipolar cells and is regulated by the metabotropic glutamate receptor mGluR6. Mutations in the genes encoding these proteins (Trpm1 and mGluR6) both produce CSNB, but the two genetic disruptions have different effects on retinal physiology. The research team compared Trpm1 knockout (KO) mice with mGluR6 KO mice to pinpoint circuit differences that produce spontaneous oscillations.
Using whole‑cell patch clamp recordings from retinal neurons and in silico network modeling, the investigators characterized synaptic inputs to RGCs and tested how removing TRPM1 changes network behavior. They also used pharmacological blockers to dissect the roles of chemical synapses and electrical coupling through gap junctions.
Key findings
In Trpm1 KO retina, excitatory and inhibitory synaptic inputs to RGCs oscillate in anti‑phase: ON and OFF pathways generate rhythmic activity that is temporally opposed, producing a pronounced oscillatory pattern in RGC firing. Blocking specific elements of the AII amacrine cell pathway or interrupting gap junction coupling suppressed the oscillations, identifying the disrupted rod bipolar cell (RBC)–AII amacrine cell circuit as the core source.
The team also documented structural remodeling in the Trpm1 KO retina. Rod bipolar cell axon terminals were smaller and mispositioned, resembling changes reported in the rd1 mouse model of retinitis pigmentosa. These morphological changes coincided with a more hyperpolarized resting membrane potential in RBCs, which weakens their output to AII amacrine cells and destabilizes the network.
Computational simulations that incorporated the observed anatomical and electrical changes reproduced the oscillatory firing patterns seen experimentally. The models indicate that even modest reductions in synaptic strength from RBCs and ON cone bipolar cells onto AII amacrine cells, together with hyperpolarization of ON bipolar cells, are sufficient to induce persistent pathological oscillations in RGCs.
Implications for disease and therapy
The study links TRPM1 deficiency to a shared circuit mechanism that can explain oscillations observed in both congenital night blindness and degenerative conditions like RP. As Prof. Chieko Koike notes, spontaneous oscillatory activity adds neural “noise” that can mask visual signals and even produce hallucinatory percepts. Therefore, therapies aimed at restoring visual input—whether gene therapy, regenerative approaches, prosthetic devices, or optogenetics—should also consider how to stabilize inner retinal activity so that patients recover clear, reliable vision rather than distorted sensations.
Professor Katsunori Kitano emphasizes that small reductions in bipolar cell output may be enough to destabilize retinal circuits and trigger oscillations, highlighting the sensitivity of inner retinal networks to changes in synaptic drive and membrane potential.
Funding information
This work was supported by the Japan Society for the Promotion of Science Grants‑in‑Aid for Scientific Research (Grant Nos. 24H00747, 22KK0137, 19H01140, and 24390019), the Takeda Science Foundation, the Kobayashi Foundation, JST PRESTO, and R‑GIRO.
Key Questions Answered:
A: Deficiency of the TRPM1 ion channel in ON bipolar cells disrupts normal signaling and triggers circuit changes that produce persistent oscillations.
A: Loss of TRPM1 weakens communication from rod bipolar cells to AII amacrine cells and creates anti‑phase oscillatory interactions between ON and OFF pathways, which drives RGC oscillations.
A: Oscillations act as neural noise that can mask or distort restored visual signals. Successful therapies will need strategies to suppress or stabilize such network activity in addition to restoring photoreceptor function.
Editorial Notes
- This article was prepared by an editor specializing in neuroscience news.
- The original journal paper was reviewed in full by the editorial team.
- Additional explanatory context was provided by editorial staff to clarify implications for therapy and research.
About this genetics and visual neuroscience research news
Author: Yuhki Nakajima
Source: Ritsumeikan University
Contact: Yuhki Nakajima – Ritsumeikan University
Image: The image is credited to Neuroscience News
Original Research: Open access. “A mechanism for pathological oscillations in mouse retinal ganglion cells in a model of night blindness” by Sho Horie et al., Journal of General Physiology. DOI available in the original publication.
Abstract (condensed)
TRPM1 channels at the dendrites of ON bipolar cells, regulated by mGluR6, are essential for normal visual signal transduction. Both Trpm1 and mGluR6 knockout mice model congenital stationary night blindness, but robust spontaneous oscillations in retinal ganglion cells are observed only in Trpm1 KO retinas. Using whole‑cell clamp recordings, morphological analysis, and computational modeling, the study shows that anti‑phase excitatory and inhibitory inputs, weakened RBC→AII AC transmission, RBC axon terminal remodeling, and hyperpolarized bipolar cell membrane potentials together produce pathological RGC oscillations. These findings indicate a shared circuit mechanism that may underlie oscillations in diverse outer retinal diseases and highlight the need to address inner retinal instability when developing vision restoration strategies.