Perforant pathway

In the brain, the perforant path is the main input to the hippocampus, arising mostly in the entorhinal cortex and terminating in the dentate gyrus.

In rats, pyramidal and stellate cells in layer II of entorhinal cortex project through the subiculum of the hippocampus, giving rise to the name "perforant pathway". These glutamatergic fibers form a laminar pattern and terminate in the dentate gyrus and cornu ammonis 3 (CA3) region of the hippocampus. Fibers arising in the lateral portions of the entorhinal cortex show enkephalin immunoreactivity, whereas medial portions appear to contain cholecystokinin. Additionally, pyramidal cells in layer III of the entorhinal cortex send topographic projections along the perforant pathway which branch into the subiculum and CA1.

In mice, the projection to CA3, CA1, and the subiculum all come primarily from EC layer III.

Reference

 * Shepherd, GM. The Synaptic Organization of the Brain.  New York:  Oxford University Press.  1998.