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Structural synaptic correlate of long‐term potentiation: Formation of axospinous synapses with multiple, completely partitioned transmission zones
Author(s) -
Geinisman Yuri,
DetoledoMorrell Leyla,
Morrell Frank,
Heller Richard E.,
Rossi Marvin,
Parshall Robert F.
Publication year - 1993
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.450030405
Subject(s) - long term potentiation , postsynaptic potential , neuroscience , perforant path , dentate gyrus , ltp induction , neurotransmission , synaptic plasticity , chemistry , postsynaptic density , synapse , dendritic spine , stimulation , inhibitory postsynaptic potential , excitatory postsynaptic potential , hippocampus , biology , hippocampal formation , receptor , biochemistry
Synapses were analyzed in the middle molecular layer (MML) and inner molecular layer (IML) of the rat dentate gyrus following the induction of long‐term potentiation (LTP) by high‐frequency stimulation of the medial perforant path carried out on each of 4 consecutive days. Potentiated animals were sacrificed 1 hour after the fourth high frequency stimulation. Stimulated but not potentiated and implanted but not stimulated animals served as controls. Using the stereological disector technique, unbiased estimates of the number of synapses per postsynaptic neuron were differentially obtained for various subtypes of axospinous junctions: For atypical (giant) nonperforated synapses with a continuous postsynaptic density (PSD), and for perforated ones distinguished by (1) a fenestrated PSD and focal spine partition, (2) a horseshoe‐shaped PSD and sectional spine partition, (3) a segmented PSD and complete spine partition(s), and (4) a fenestrated, (5) horseshoe‐shaped, or (6) segmented PSD without a spine partition. The major finding of this study is that the induction of LTP in the rat dentate gyrus is followed by a significant and marked increase in the number of only those perforated axospinous synapses that have multiple, completely partitioned transmission zones. No other synaptic subtype exhibits such a change as a result of LTP induction. Moreover, this structural alteration is limited to the terminal synaptic field of activated axons (MML) and does not involve an immediately adjacent one (IML) that was not directly activated by potentiating stimulation. The observed highly selective modification of synaptic connectivity involving only one particular synaptic subtype in the potentiated synaptic field may represent a structural substrate of the long‐lasting enhancement of synaptic responses that characterizes LTP.