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Reduction of background autofluorescence in brain sections following immersion in sodium borohydride
1Department of Psychology, Cornell University, Ithaca, NY 14853, USA. bec8@cornell.edu
Abstract:
Autofluorescence of aldehyde-fixed neural tissue often obscures perikaria and fine processes labeled with fluorescent anterograde or retrograde tracers. In particular, this autofluorescence hinders the detectability of fine axonal projections labeled with the convenient anterograde tracer, tetramethylrhodamine dextranamine. Background fluorescence was notably reduced by immersion of free-floating brain tissue sections in a solution of sodium borohydride (NaBH4, 0.1%), a chemical which is known to neutralize Schiffs bases through reduction of amine-aldehyde compounds into non-fluorescent salts. The reversible and renewable immersion technique was most effective in paraformaldehyde-fixed tissue where the preservation quality was improved such that labeled axons remained detectable for more than 1 year after initial preparation.
Insights
Autofluorescence in neural tissue obscures fluorescent tracers. Treating aldehyde-fixed brain sections with sodium borohydride (NaBH4) effectively reduces this background fluorescence, improving tracer detectability.
Area of Science:
- Neuroscience
- Histology
- Biochemistry
Background:
- Autofluorescence in aldehyde-fixed neural tissue obscures fluorescently labeled neuronal structures.
- This background fluorescence particularly hinders the detection of fine axonal projections labeled with tracers like tetramethylrhodamine dextranamine.
Purpose of the Study:
- To develop a method for reducing autofluorescence in aldehyde-fixed neural tissue.
- To enhance the detectability of fluorescently labeled neuronal pathways.
Main Methods:
- Immersion of free-floating brain tissue sections in a 0.1% sodium borohydride (NaBH4) solution.
- Utilizing NaBH4's known property to reduce Schiff bases, neutralizing amine-aldehyde compounds.
Main Results:
- Sodium borohydride (NaBH4) immersion significantly reduced background autofluorescence in neural tissue.
- The technique was most effective in paraformaldehyde-fixed tissue.
- Labeled axons remained detectable for over 1 year after treatment, indicating preserved tissue quality.
Conclusions:
- Sodium borohydride treatment is an effective, reversible, and renewable method to reduce autofluorescence in fixed neural tissue.
- This technique improves the detectability of fluorescently labeled neuronal structures, especially fine axonal projections.
- The method enhances long-term preservation and visibility of neural tracers in histological preparations.