A direct projection from the perirhinal cortex (area 35) to the subiculum in the rat.

An efferent projection from the perirhinal cortex (area 35) in the rat was studied using the anterograde transport of tritiated amino acids as well as horseradish peroxidase (HRP). Following injections of either tracer in either the dorsal or ventral parts of area 35, anterogradely transported label was observed in the molecular layer of the subiculum, adjacent prosubiculum and CAla. Regardless of the dorsoventral level of the injection, the label was most dense at mid-dorsoventral levels of the subiculum and decreased in density in both the septal and temporal directions. Small injections of the same tracers made into the surrounding entorhinal, ectorhinal or prepiriform cortices did not reproduce this pattern. While the entorhinal cortex is the main cortical source of afferent input to the molecular layer of the subiculum as well as the hippocampus and dentate gyrus, the perirhinal cortex appears to constitute a complementary cortical pathway for afferent input to the subiculum.