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Updated: Feb 9, 2026

Transretinal ERG Recordings from Mouse Retina: Rod and Cone Photoresponses
Published on: March 14, 2012
Contrary to popular belief, chinchillas do not have a pure rod retina
Shai Sandalon1, Anna Boykova2, Maya Ross1
1Koret School of Veterinary Medicine, Hebrew University of Jerusalem, Rehovot, Israel.
Purpose:
To establish whether there is cone contribution to retinal function and structure in chinchillas (Chinchilla lanigera), in view of the prevailing notion that this species possesses a pure rod retina.
Methods:
Photopic electroretinography (ERG) responses to high-intensity flashes (10 and 25 cd*s/m2 ) were recorded unilaterally in six pigmented chinchillas following 10 minutes of light adaptation (30 cd/m2 ). Retinas of two animals were studied histologically, and immunohistochemistry (IHC) was conducted to detect the presence of short and medium/long wavelength cone photoreceptors.
Results:
ERG recordings revealed photopic responses, albeit of low amplitudes. Histopathology demonstrated presumptive cone inner segments in the photoreceptor layer. Presence of cone photoreceptors was confirmed by IHC. Cone density was higher in the central retina, and red/green cones outnumbered blue cones.
Conclusions:
Our results provide convincing evidence for the presence of functioning cone photoreceptors in the chinchilla retina, disproving the established belief that the species has a pure rod retina.
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According to its composition, the matter can be classified into two broad categories — pure substances and mixtures.
A pure substance is a form of matter that has a constant composition throughout with uniform properties. For example, any sample of sucrose has the same composition and same physical properties, such as melting point, color, and sweetness, regardless of the source from which it is isolated.
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