A modification of the rapid glyoxylic acid technique permits visualization of serotonergic and hypothalamic...

The rapidity, simplicity and reproducibility of the rapid glyoxylic acid technique (SPG) has made it the method of choice for many investigators interested in the histofluorescence of CNS catecholamine systems. Unfortunately, the serotonergic system and the dopaminergic hypothalamic cell groups are poorly visualized with this method. Using intraventricular colchicine pretreatment, reliable visualization of these systems can be obtained. The serotonergic fluorescence seen with colchicine administration is augmented by l-tryptophan pretreatment and diminished by pretreatment with para-chlorophenylalanine, a tryptophan hydroxylase inhibitor. It is relatively resistant to fading under ultra-violet illumination and photographs can be taken up to 4 weeks after the sections have been processed. Visualization of dopaminergic, hypothalamic neurons as well as visualization of the dendritic fields of all catecholaminergic neurons is comparable to that obtained with tyrosine hydroxylase immunocytohistochemistry.