The well‐known alpha retinal ganglion cells
Authors: Avilés‐Trigueros Marcelino 
Published: January 2025

Understanding the structure, function, and significance of retinal ganglion cells (RGCs) is essential for untangling the complexities of visual perception and for developing targeted treatments for retinal diseases and disorders.

Recent studies in mice point to over 40 different types of RGC based on their morphology, size, functionality, or molecular features. Among these, alpha‐RGCs (αRGCs), also known as type A, have been extensively studied. These cells stand out due to their relatively large soma size compared to other types of RGCs, like beta and gamma cells. They typically show well‐defined dendritic arborization and axons, with mono‐stratified dendritic branches extending into different layers of the inner plexiform layer (IPL) and high levels of neurofilament proteins.

The dendrites of αRGCs cover large receptive fields in specific regions of the retina, dictating where they receive visual inputs. These cells share common physiological, such as short response latency and fast‐conducting axons, allowing them to quickly respond to new stimuli. αRGCs can be functionally categorized into ON and OFF canters, responding to light intensity increases (ON) and decreases (OFF) within their receptive field centers, which also corresponds to the anatomical dendritic layering in the IPL. These responses can also be subdivided into sustained or transient, aligning with dendritic distribution in sustained or transient IPL regions.

Currently, four subtypes of αRGCs have been shown based on their receptive fields, signal patterns, and their mono‐stratification into the IPL: ON‐sustained (ONs‐αRGCs), ON‐transient (ONt‐αRGCs), OFF‐sustained (OFFs‐αRGCs) and OFF‐transient (OFFt‐αRGCs).

The combined use of specific antibodies helps in the identification and study of αRGCs and their subtypes, which is crucial to know their distribution and the number of this cell population and its subtypes in the retina. The use of simple immunohistochemical protocols and image analysis techniques to identify each of the αRGC subtypes makes it possible to characterize the topographic distribution patterns and to know the total number of each of these subtypes in the retina. This approach may be relevant in the study of the response of each of these cell types to a retinal pathology or a specific treatment.

These cells are distributed across the retina, with higher density in the temporal area. Sustained ON and OFF response subtypes are mainly located in the periphery while the transient ON and OFF response subtypes are found in the central regions of the retina.

αRGCs represent a crucial component of the visual system, contributing to essential visual functions, neural pathways, and adaptive processes. Their structural and functional characteristics make them key players in visual perception, and understanding their roles in health and disease is essential for advancing both basic neuroscience research and clinical ophthalmology. Continued research into αRGCs holds promise for developing novel therapies aimed at preserving vision and improving outcomes for individuals with retinal disorders.