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Synaptic alterations in the dentate gyrus molecular layer after repeated administration of electroconvulsive shock seizures
Author(s) -
Assunção Marco,
Pereira Pedro,
Lukoyanov Nikolai
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1416-a
Subject(s) - dentate gyrus , hippocampal formation , excitatory postsynaptic potential , electroconvulsive shock , neuroscience , hippocampus , chemistry , stereology , medicine , anesthesia , biology , receptor
Electroconvulsive shock (ECS) is widely used in animal studies as a model of brief generalized seizures. It has been recently shown that repeated ECS seizures cause a number of subtle morphological alterations in the hippocampal formation of adult rats. We have earlier reported that ECS treatment causes a loss of cells in the hilus of the dentate gyrus. In the present work, we decided to study the effect of repeated administration of ECS on the number of axo‐spinous and axo‐dendritic synapses in the molecular layer of the dentate gyrus. Ten 8‐week old male Wistar rats were used in this study. Five rats received a course of six ECS seizures via ear‐clip electrodes, the first five of which were given 24 h apart, whilst the last two were spaced by a 2‐h interval. Remaining five rats constituted a sham‐treated control group. The number of synapses was estimated using stereological methods including the physical disector and the principle of Cavalieri. ECS treatment resulted in an increase of the volume density of synapses in the inner molecular layer but not in the outer molecular layer. However, because ECS treatment additionally produced a dramatic reduction in the total volume of the dentate molecular layer, the total number of synapses estimated either in the outer molecular layer or in the inner one was found to be significantly lower in ECS‐treated animals when compared with control rats. These results suggest that ECS, when administered repeatedly, can reduce the excitatory drive arriving to the dentate gyrus from the enthorinal cortex and from the contralateral hippocampal formation. These data also support the earlier findings that repeated ECS seizures cause a compensatory sprouting of the mossy fibers into the dentate inner molecular layer. Granted by Unit 121/94 and SFRH/BD/19497/2004 from FCT.