High resolution radioautography of central dopaminergic fibers labelled in vitro with [3H]dopamine or [3H]norepinephrine.

An original method is reported for the radioautographic visualizing of dopaminergic axons terminals in the rat central nervous system. This method is based on an in vitro labelling with either tritiated norepinephrine or dopamine under conditions of specificity previously established by fluorescence histochemistry. The immobilization of [3H]catecholamines in their sites of uptake and storage during post-fixation for electron microscopic processing was ensured by the use of osmic acid vapours instead of osmic acid solution. Selective labelling of the dopaminergic fibers may be achieved throughout large brain sections and the technique should be applicable to human biopsy material.