We have used Sudan Black injections as a stain to verify cannula placements:
0.3g Sudan Black B in 100 ml 70% Ethanol (then filter), inject 0.4 ul for site specific injections.
The rational for the use of Sudan Black is that it is lipophilic and will stain neuronal membranes well, and stays in the tissue even after perfusion.
It can also be used to suppress tissue autofluoresence, but I do not think we found it very helpful in our hands.
Double immunolabeling of neuropeptides in the human hypothalamus as analyzed by confocal laser scanning fluorescence microscopy. Romijn HJ1, van Uum JF, Breedijk I, Emmering J, Radu I, Pool CW., J Histochem Cytochem. 1999 Feb;47(2):229-36.
Sudan Black B treatment reduces autofluorescence and improves resolution of in situ hybridization specific fluorescent signals of brain sections. Oliveira VC1, Carrara RC, Simoes DL, Saggioro FP, Carlotti CG Jr, Covas DT, Neder L. Histol Histopathol. 2010 Aug;25(8):1017-24.
K. Burdon, J. Stokes, and C. Kimbrough. “Studies of the common aerobic spore-forming bacilli.” Journal of Bacteriology 43(6):717-724, 1941
(Burdon has another technique paper: K. Burdon. “Fatty material in bacteria and fungi revealed by staining dried, fixed slide preparations.” Journal of Bacteriology 52(6):665-678, 1946.)