Rapid photoresponses were obtained from the pineal organ ofRana catesbeiana andRana esculenta comparable to the early receptor potential (ERP) of the retina of their lateral eyes.
Light source was a xenon filled discharge tube with a maximum energy input of 365 J. The flash duration was 600 μsec measured at 1/3 peak amplitude.
The response pattern of the ERP of the exposedEpiphysis cerebri (intracranial portion of the frog's pineal organ) resembled the ERP of the isolated retina and the R1 deflection of the ERP of the eye-cup. It was greatly diminished during consecutive flashes and was absent during light adaptation. It was confined to theEpiphysis cerebri and was similar in time course and shape to, though smaller as, the ERP of the isolated retina.
The photoresistant component of the ERP in the eye-cup was lacking in theEpiphysis cerebri and in the isolated retina.
The action spectrum of the ERP of theEpiphysis cerebri closely resembled the photopigment absorption of rhodopsin indicating that the structural cones of the pineal organ contain a photopigment different from the retinal cones of the frog's lateral eye.
Key wordsEarly Receptor Potential Pineal Organ Photoreceptor Photopigment Cones Action Spectrum Epiphysis cerebri
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