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A Remarkable Tale: Increased Retinal Fluorescence Following Application of Permanent Marker Ink to Mouse Tails.

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Red marker ink contains Rhodamine 6G (R6G), a fluorescent component that can be orally ingested by mice. This leads to retinal fluorescence, impacting experimental identification and offering potential imaging applications.

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Area of Science:

  • Ophthalmology
  • Neuroscience
  • Toxicology

Background:

  • High retinal fluorescence was observed in mice marked with red ink.
  • Mice were seen licking ink from their tails, suggesting oral intake.
  • Rhodamine 6G (R6G) in red ink was hypothesized as the cause.

Purpose of the Study:

  • To investigate if red marker ink, specifically Rhodamine 6G (R6G), causes retinal fluorescence after oral ingestion in mice.
  • To assess the dose-dependent effects and time course of R6G-induced retinal fluorescence.
  • To explore potential applications and experimental considerations related to R6G fluorescence.

Main Methods:

  • Mice were tail-marked with varying amounts of red ink.
  • In vivo confocal scanning laser ophthalmoscope (cSLO) imaging monitored retinal fluorescence.
  • Histological analysis of retinas and brains was performed.
  • A separate group received oral gavage of R6G.

Main Results:

  • Tail marking with red ink caused a transient, dose-dependent increase in retinal fluorescence, peaking at 6 hours.
  • Histology showed R6G fluorescence primarily in photoreceptor outer segments.
  • Oral R6G administration replicated this fluorescence localization.
  • Brain fluorescence was observed in the choroid plexus and ventricles.

Conclusions:

  • Rhodamine 6G (R6G) can penetrate the gut-blood, blood-retina, and blood-cerebrospinal fluid barriers.
  • This finding has implications for mouse experimental identification methods.
  • Potential applications exist for fluorescence imaging and targeted drug delivery to the central nervous system.