Morphological details of the projection from the presubiculum to the entorhinal area as shown with the novel PHA-L immunohistochemical tracing method in the rat.

Iontophoretic injections of the lectin, phaseolus vulgaris leucoagglutinin (PHA-L) were made into the presubiculum of rats. The anterogradely transported lectin was visualized by using an anti-PHA-L antibody in combination with immunohistochemistry. The PHA-L tracing method revealed morphological details of the projection of the presubiculum to the ipsi- and contralateral medial entorhinal area usually not seen with other anterograde transport techniques. Fine varicose fibers form a dense terminal plexus in the deep parts of layer III. In layer II and deep layer I, the fibers form column-like axonal bundles, terminating in patches in the deep part of layer I. Some fibers reach the outer three layers of the entorhinal area (EA) from collaterals of axons running in the molecular layer, while a majority enter from the deep layers.