An indicator of individual retinal receptor response in the mammal is sought. This indicator must represent a detectable physical or chemical change of state in the receptor induced by the transducer of the photoreceptor. A histochemical technique has recently been described which results in differential staining between light-adapted and dark-adapted receptors.
In this experiment an attempt has been made to identify the action spectrum of this reaction in the predominantly rod retina of the albino rat. The action spectrum of this differential staining effect approximates that of rhodopsin.
The staining takes place in the ellipsoid portion of the receptor (in the inner segment). From other investigations, however, rhodopsin is known to be localized in the outer segments of such cells.
JAY M. ENOCH, "Validation of an Indicator of Mammalian Retinal Receptor Response: Action Spectrum," J. Opt. Soc. Am. 54, 368-374 (1964)