Abstract
The use of Procion Yellow (M-4RS, ICI America, Inc.) as a fluorochrome in conjunction with catecholamine-derived isoquinoline fluorescence is examined by chemical techniques. From a series of chemical studies it has been found that: (a) Procion Yellow does not interfere with the formation of isoquinoline derivatives of catecholamine; (b) commercially available Procion Yellow is a composite of four species, all of whose emission-excitation maxima are distinguishable from that of catecholamine-derived isoquinohines; and (c) the emission-excitation maxima of Procion Yellow and of the catecholamine-derived isoquinolines are distinguishable one from another in solution. It is suggested that Procion Yellow can be a valuable fluorochrome to use in conjunction with the histofluorometric method. The data support the possibility that single adrenergic neuronal cells after being tagged with Procion Yellow can subsequently be shown to contain biogenic amines.