Entorhinal cortex projection cells to the hippocampal formation in vitro

Retrogradely labeled cells in superficial and deep layers of the entorhinal cortex (EC) were analyzed following application of the fluorescent tracer rhodamine-dextran-amine in different sites of the hippocampal formation in a slice preparation. The results demonstrate a strong projection from layer IV/V to the dentate gyrus, that is in slices significantly stronger than that from layer II. In deep layers a large number of multipolar cells were found which were only labeled by dye application to the subiculum. Patch-clamp recordings from these cells revealed intrinsic low threshold membrane potential oscillations, suggesting their possible contribution to oscillatory network activity of the EC and subiculum.