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Convergence of entorhinal and CA3 inputs onto pyramidal neurons and interneurons in hippocampal area CA1—An anatomical study in the rat
Author(s) -
Kajiwara Riichi,
Wouterlood Floris G.,
Sah Anupam,
Boekel Amber J.,
Bakste Bulte Luciënne T.G.,
Witter Menno P.
Publication year - 2008
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/hipo.20385
Subject(s) - perforant path , neuroscience , perforant pathway , hippocampal formation , entorhinal cortex , dentate gyrus , pyramidal cell , hippocampus , schaffer collateral , interneuron , anatomy , chemistry , biology , excitatory postsynaptic potential , inhibitory postsynaptic potential
The entorhinal cortex (EC) conveys information to hippocampal field CA1 either directly by way of projections from principal neurons in layer III, or indirectly by axons from layer II via the dentate gyrus, CA3, and Schaffer collaterals. These two pathways differentially influence activity in CA1, yet conclusive evidence is lacking whether and to what extent they converge onto single CA1 neurons. Presently we studied such convergence. Different neuroanatomical tracers injected into layer III of EC and into CA3, respectively, tagged simultaneously the direct entorhino‐hippocampal fibers and the indirect innervation of CA1 neurons by Schaffer collaterals. In slices of fixed brains we intracellularly filled CA1 pyramidal cells and interneurons in stratum lacunosum‐moleculare (LM) and stratum radiatum (SR). Sections of these slices were scanned in a confocal laser scanning microscope. 3D‐reconstruction was used to determine whether boutons of the labeled input fibers were in contact with the intracellularly filled neurons. We analyzed 12 pyramidal neurons and 21 interneurons. Perforant path innervation to pyramidal neurons in our material was observed to be denser than that from CA3. All pyramidal neurons and 17 of the interneurons received contacts of both perforant pathway and Schaffer input on their dendrites and cell bodies. Four interneurons, which were completely embedded in LM, received only labeled perforant pathway input. Thus, we found convergence of both projection systems on single CA1 pyramidal and interneurons with dendrites that access the layers where perforant pathway fibers and Schaffer collaterals end. © 2007 Wiley‐Liss, Inc.