The in situ detectability of the neuroanatomical tracer Phaseolus vulgaris-leucoagglutinin (PHA-L).

We determined the in situ detectability of the neuroanatomical tracer Phaseolus vulgaris-leucoagglutinin (PHA-L). The tracer was bilaterally injected in the nucleus accumbens of the ventral striatum of young adult rats. After post-injection survival periods ranging from 4.5 to 16 weeks, sections of the brain were subjected to immunocytochemical detection of the transported PHA-L. We examined the labelled neurons in the injection sites, the labelled local and efferent fibres, and the labelled terminal structures in the ventral pallidum. Up to 4.5 weeks after the injection, the PHA-L-labelled neurons in the injection site were completely stained and displayed dendrites with numerous spines. There was also good visualization of local axonal plexuses and of the efferent fibres and their varicosities along the trajectories to and in the termination areas. Six and a half weeks after the injection, the fibres coursing from the injection site to the termination area were difficult to visualize. By contrast, the injection site contained labelled cell bodies, dendrites with few spines, weakly stained fibres, and punctate labelling. In the termination areas there was a clear, punctate terminal labelling in addition to weak fibre labelling. Between 8 and 10 weeks after the injection, labelled neurons in the injection site could be visualized as well as a cloud of punctate staining in the termination area, but labelled fibres and dentritic spines were not observed. Eleven weeks after the injection, label was no longer demonstrable in terminals. After survival periods of 13 weeks and longer, the only labelled structures were weakly PHA-L-immunoreactive perikarya at the injection site, surrounded by punctate labelling.(ABSTRACT TRUNCATED AT 250 WORDS)