Cryostat technique for central nervous system histofluorescence

This paper offers a technique for obtaining monoamine histofluorescence in the CNS by means of formaldehyde perfusion followed by cryostat sectioning. No freeze-drying is involved. Cryostat sections are exposed to formaldehyde vapor to complete the fluorophore formation. The fluorescence thus obtained is bright, well localized, and does not require loading the animals with precursors. The anatomical distribution of the pathways is identical to that obtained with the classical technique. Furthermore, the fluorescence is reversible by sodium borohydride, and exhibits the expected changes in intensity with pharmacological manipulations. The sections can be exposed to a cold aqueous medium for as long as 15 min with minimal diffusion of fluorophore; this suggests potential for combining monoamine histofluorescence with other visualization techniques.