A Novel Entorhinal Projection to the Rat Dentate Gyrus: Direct Innervation of Proximal Dendrites and Cell Bodies of Granule Cells and GABAergic Neurons

摘要: Entorhinal fibers to the fascia dentata originating from layer II stellate neurons are known terminate exclusively in outer two thirds of molecular layer, where they innervate distal dendritic portions dentate neurons. Using anterograde tracing with Phaseolus vulgaris leucoagglutinin, we unraveled a previously unknown entorhinal projection that directly innervates proximal and somata granule cells GABAergic This originates located layers IV–VI medial area. These enter traverse inner (IML) cell form numerous boutons, finally arborize subjacent cells. Correlated light electron microscopy revealed boutons formed by these establish asymmetric synapses on dendrites IML, spines cells, spineless layer. Postembedding immunogold staining indicates this entorhino-dentate is not it also terminates inhibitory data demonstrate all display similar high laminar specificity for (OML). Although superficial cortex OML, arising deeper confined boundaries. Finally, possibility supposedly excitatory afferents may monosynaptically activate needs be incorporated into contemporary concepts hippocampal network.