Evidence for an anterograde transport of the fluorescent tracer Fast Blue in the strio-nigro-striatal loop of the rat.

The report is concerned with serendipitous observations which were made in the course of investigations on the connectivity of the claustrum. Stereotaxical injections of Fast Blue were made in the neostriatum. All major sources of striopetal fiber systems were found to contain fluorescent cell bodies. Quite unexpectedly, also fluorescent axons and terminals could be observed in brain regions known to receive a striofugal input including the globus pallidus, entopeduncular and subthalamic nucleus, and the substantia nigra, zona reticulata. It is concluded that Fast Blue may be used for both retrograde and anterograde neuronal tracing.