A Method for Counterstaining Tissues in Conjunction with the Glyoxylic Acid Condensation Reaction for Detection of Biogenic Amines

A method is described for counterstaining tissue for use with the glyoxylic acid reaction for visual detection of biogenic amines. Counterstaining is achieved by addition of the fluorescent dye malachite green to the sucrose-phosphate-glyoxylic acid (SPG) solution used for processing of cryostat sections of unfixed tissues. When bound to tissues, the dye provides red-orange fluorescence of background tissue, which contrasts well with the green to yellow fluorescence induced by the glyoxylic acid reaction product formed with biogenic amines. The counterstaining technique is demonstrated in a number of catecholamine-containing peripheral tissues and is compared to sections that were processed without counterstaining.