Biophotons Contribute to Retinal Dark Noise
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The discovery of dark noise in retinal photoreceptors resulted in a long-lasting controversy over its origin and the underlying mechanisms. Here, we used a novel ultra-weak biophoton imaging system (UBIS) to detect biophotonic activity (emission) under dark conditions in rat and bullfrog (Rana catesbeiana) retinas in vitro. We found a significant temperature-dependent increase in biophotonic activity that was completely blocked either by removing intracellular and extracellular Ca2+ together or inhibiting phosphodiesterase 6. These findings suggest that the photon-like component of discrete dark noise may not be caused by a direct contribution of the thermal activation of rhodopsin, but rather by an indirect thermal induction of biophotonic activity, which then activates the retinal chromophore of rhodopsin. Therefore, this study suggests a possible solution regarding the thermal activation energy barrier for discrete dark noise, which has been debated for almost half a century.
KeywordsBiophoton Rat and bullfrog retinas Retinal dark noise Phosphodiesterase 6 Ca2+ Biophoton imaging
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