A modified glyoxylic acid-formaldehyde technique for histofluorescence of catecholamine-containing neurons in cryostat sections of the insect brain.

A simple and rapid method is described to demonstrate catecholamine-containing neurons in the insect brain by cryostat sectioning and immersion in an ice-cold SPG (sucrose-potassium phosphate-glyoxylic acid) solution. The fluorescent yield achieved can be further intensified by heating the preparations with formaldehyde vapors. The advantages of the method as compared to the original Falck-Hillarp method are speed, simplicity, and a very distinct photostabile fluorophore. The preparations can be stored for several weeks. The drawback is a lower sensitivity than the Falck-Hillarp method provides.