Related Experiment Video
Updated: Apr 7, 2026
08:38
Transretinal ERG Recordings from Mouse Retina: Rod and Cone Photoresponses
Published on: March 14, 2012
18.5K
Melatonin modulates M4-type ganglion-cell photoreceptors
1Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, MI 48105, United States.
Neuroscience
|July 5, 2015
Summary
Melatonin modulates intrinsically photosensitive retinal ganglion cells (ipRGCs) in the retina. This study reveals circadian control over M4-type ipRGCs and their responses to light.
Area of Science:
- Neuroscience
- Retinal Physiology
- Circadian Biology
Background:
- Melatonin, secreted by retinal photoreceptors at night, acts as a dark-adaptive signal.
- Melatonin receptors are present in retinal neurons, including intrinsically photosensitive retinal ganglion cells (ipRGCs).
- ipRGCs, particularly M4-type cells, are involved in both image-forming and non-image-forming visual functions.
Purpose of the Study:
- To investigate the modulatory effects of melatonin on alpha-like M4-type ipRGCs.
- To determine if melatonin influences rod/cone-driven and melanopsin-based light responses in M4 ipRGCs.
- To explore the circadian control of M4 ipRGCs' properties and responses.
Main Methods:
- Whole-cell electrophysiology was used to record light responses from M4 ipRGCs.
- Melatonin was applied during daytime, and a melatonin receptor antagonist (luzindole) was applied during nighttime.
- Immunohistochemistry was performed to detect MT1 melatonin receptors in M4 cells.
Main Results:
- Daytime melatonin application broadened and enlarged rod/cone-driven photoresponses in M4 cells, reducing spike rate.
- Melanopsin-based light responses were not significantly affected by melatonin.
- Nighttime luzindole application reversed these effects, confirming endogenous melatonin modulation and indicating circadian variations in M4 cell properties.
Conclusions:
- Melatonin modulates rod/cone-driven responses in M4 ipRGCs, potentially via direct action on MT1 receptors.
- M4 ipRGCs exhibit circadian control, with distinct resting properties and light responses between day and night.
- This study is the first to report circadian variations in ipRGCs and melatoninergic modulation of these cells.
Related Concept Videos
01:02The Pineal Gland
7.7K
The pineal gland, a diminutive endocrine structure named for its pinecone-shaped appearance, is situated atop the third ventricle within the diencephalon region of the forebrain. This gland, composed of secretory cells known as pinealocytes arranged in compact cords and clusters around dense particles of calcium salts, plays a pivotal role in hormonal regulation.
The primary secretion of the pineal gland is the hormone melatonin, derived from serotonin. The concentration of melatonin in the...
The primary secretion of the pineal gland is the hormone melatonin, derived from serotonin. The concentration of melatonin in the...
7.7K
01:19Management of Insomnia
785
The sleep cycle, an integral part of human health, consists of several stages with distinct characteristics and functions. It begins with a transition from wakefulness to sleep, known as the light sleep phase, followed by the restorative deep sleep phase, essential for physical recovery and growth. The cycle concludes with the Rapid Eye Movement (REM) phase, characterized by high brain activity and vivid dreaming. Insomnia, a prevalent sleep disorder, involves difficulty falling asleep, staying...
785
01:22Photoreceptors and Visual Pathways
11.1K
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,...
11.1K
01:21G-Protein Gated Ion Channels
7.1K
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...
Sensory...
7.1K
01:32The Retina
78.7K
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.
78.7K
02:19Circadian Rhythms and Gene Regulation
4.7K
The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent...
4.7K