Figure 4.

MEC lesions were validated by loss of retrograde FG labeling. FG was injected into comparable levels of the dorsal CA1 of a TC animal (A), or a MEC lesioned animal (B) one week after the lesion operation occurred. In the TC animal, MEC layer III and CA3 pyramidal cells were retrogradely labeled with FG, as expected. Strong labeling is also visible in the presubiculum (PrS). Creating an excitotoxic lesion in MEC, however, resulted in attenuated labeling of MEC layer III cells. As expected, cells in CA3 were still labeled, indicating that lack of MEC label is not due to poor FG transport. The Nissl stain of the section is shown in the lower right. MEC starts at the solid line and arrows indicate the medio-lateral extent of the lesion (layers II, III, and top of layer V). CA1, cornu ammonis area 1; CA3, cornu ammonis area 3; DG, dentate gyrus; SUB, subiculum; HPC, hippocampus; PaS, Para subiculum; MEC, medial entorhinal cortex; and II, III, and V/VI, layers II, III, and V/VI of MEC. Delineations of the areas were based on the Nissl stains of the sections.