Abstract
Fluorophores induced from noradrenaline and dopamine in tissue sections by treatment with formaldehyde can be separated by their different behavior upon HCl treatment. The noradrenaline fluorophore converts to a fully aromatic isoquinoline while the dopamine fluorophore remains in the form of a nonquinoidal dihydroisoquinoline. The two fluorophores have readly distinguishable excitation spectra. The procedure has been tested both in model systems and in tissue sections. The microspectrofluorometer used is described.