Microiontophoretic injection of fluorescent tracer combined with simultaneous immunofluorescent histochemistry for the demonstration of efferents from the caudate-putamen projecting to the globus pallidus.

Precise local injections of propidium iodide (PI) were made, using an iontophoretic technique, into various regions of the globus pallidus (GP) of rats. The locations of the injection sites and the position of retrogradely labelled caudate putamen (CP) cell bodies demonstrated a topographic arrangement of efferents from the CP projecting to the pallidum. The PI labelled cell bodies in the CP were also counterstained for met-enkephalin immunofluorescence. Cell bodies labelled with PI, which showed co-existing enkephalin immunofluorescence, were found in CP projections to the pallidum.