Related Experiment Video
Updated: Aug 15, 2026
08:38
Transretinal ERG Recordings from Mouse Retina: Rod and Cone Photoresponses
Published on: March 14, 2012
Cation selectivity of light-sensitive conductance in retinal rods
Nature
|May 24, 1984
Summary
Vertebrate photoreceptors
Area of Science:
- Vision science and cellular physiology.
- Photoreceptor cell function and signaling.
Background:
- Vertebrate photoreceptors generate a membrane hyperpolarization upon light exposure.
- This response is traditionally attributed to a decrease in sodium (Na)-selective conductance.
- A leading hypothesis involves light-induced intracellular calcium (Ca) increase blocking Na conductance, with Ca extrusion via a Na-Ca exchanger.
Purpose of the Study:
- To investigate the ionic permeability of the light-sensitive conductance in photoreceptor outer segments.
- To elucidate the role of external ions in modulating this conductance.
- To explain the observed reversal potential of the light response.
Main Methods:
- Electrophysiological recordings from photoreceptor cells.
- Ionic substitution experiments in the external solution.
- Analysis of ion permeation through the light-sensitive conductance.
Main Results:
- The light-sensitive conductance in rods is not exclusively Na-selective but is also highly permeable to potassium (K).
- External Na ions tend to keep the conductance open, while external K ions tend to close it, likely mediated by the Na-Ca exchanger.
- The conductance permits permeation by other monovalent cations (Li, Rb, Cs) and divalent cations (Ca, Sr, Ba).
Conclusions:
- The light-sensitive conductance in photoreceptors exhibits broad cation permeability, including K.
- The opposing effects of external Na and K on conductance, possibly via the Na-Ca exchanger, contribute to regulating photoreceptor response.
- The permeability to both Na and K explains the previously puzzling reversal potential of the light response at 0 to +10 mV.
Related Concept Videos
01:32The Retina
The retina is a layer of nervous tissue at the back of the eye that transduces light into neural signals. This process, called phototransduction, is carried out by rod and cone photoreceptor cells in the back of the retina.
02:00Photoreceptors and Plant Responses to Light
Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides other important cues to regulate a range of developmental and physiological responses in plants.
01:11Channel Rhodopsins
Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins.
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
01:21G-Protein Gated Ion Channels
GPCRs are primarily responsible for our sense of smell, taste, and vision. The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...
Sensory organs,...
01:20Anatomy of the Eyeball
The eye is a spherical, hollow structure composed of three tissue layers. The outer layer — the fibrous tunic, comprises the sclera — a white structure — and the cornea, which is transparent. The sclera encompasses some of the ocular surface, most of which is not visible. However, the 'white of the eye' is distinctively visible in humans compared to other species. The cornea, a clear covering at the front of the eye, enables light penetration. The eye's middle layer, the vascular tunic,...
01:22Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...