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Ultrastructure and aspects of functional organization of pyramidal and nonpyramidal entorhinal projection neurons contributing to the perforant path
Author(s) -
Germroth Peter,
Schwerdtfeger Walter K.,
Buhl Eberhard H.
Publication year - 1991
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903050205
Subject(s) - soma , neuroscience , dendritic spine , biology , perforant path , hippocampal formation , ultrastructure , anatomy , axon , excitatory postsynaptic potential , dentate gyrus , inhibitory postsynaptic potential
Identified entorhino‐hippocampal projection neurons were investigated for their ultrastructure. Spinous projection neurons (pyramidal and spiny stellate cells) display common features such as symmetric axosomatic terminals on their somata, asymmetric synapses on the spines, and both types of synapses on the dendritic shafts. Their axons descend towards the white matter, branching occasionally via collaterals which establish contact with local spines and rarely on dendritic shafts and somata. The sparsely spinous projection neurons (multipolar and horizontal‐bipolar) typically show deep nuclear infolds and symmetric and asymmetric synapses on their somata and dendritic shafts. Axons also collateralize in the soma vicinity and form local synapses. It is concluded that the entorhino‐hippocampal projection neurons (both spiny and sparsely spinous) act locally and distally thus performing simultaneously as local‐circuit and as projection neurons. In accordance with other morphological and electrophysiological reports it appears likely that the generation, modulation, and suppression of entorhinal excitation waves is mediated by these neurons through direct excitation, feed‐forward and feed‐back inhibition, and disinhibition.