Synaptic reorganization in the hippocampal formation of alcohol-fed rats may compensate for functional deficits related to neuronal loss.
We have examined the behavioral and neuroanatomical effects of long-term alcohol intake in rats ingesting a 20% solution of ethanol for 30 weeks. Previous studies have shown that this treatment provokes neuronal degeneration in the hippocampal formation, which occurs in parallel with remodeling processes. Spatial reference and working memory of alcohol-fed rats were evaluated during last 4 weeks of treatment by comparison of their performance with age-matched controls on the Morris water maze. Alcohol consumption did not affect the performance of rats in the reference memory task as indicated by the measures derived from the acquisition trials and from the probe-trial, which were highly similar for alcohol-fed and control animals. Also, performance in the working memory task was not significantly altered in alcohol-treated animals. No treatment-related changes in swim speed or impairments of sensorimotor abilities, tested in the visible platform task, were detected. Stereological methods were applied to evaluate the damage inflicted by alcohol intake in the structure of the hippocampal formation. In the alcohol-treated animals, there was a noticeable cell loss in the granular layer of the dentate gyrus (10%), and in CA3 (18%) and CA1 (19%) hippocampal subdivisions. In spite of the neuronal loss, the total number of synapses between mossy fibers and CA3 pyramids was unaffected by alcohol treatment suggesting that new synaptic contacts were formed between the surviving neurons. We show that, regardless the marked hippocampal cell loss in rats exposed to chronic alcohol intake, the reorganization that takes place at the synaptic level may alleviate the expected functional deficits.
Lukoyanov
N V
NV
Department of Anatonmy, Porto Medical School, Alameda Prof. Hernâni Monteiro, Portugal. luk@med.up.pt
Brandão
F
F
Cadete-Leite
A
A
Madeira
M D
MD
Paula-Barbosa
M M
MM
D000428:Alcohol Drinking / Q000473:pathology* / Q000523:psychology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002452:Cell Count; D003712:Dendrites / Q000473:pathology; D006624:Hippocampus / Q000473:pathology*; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D019599:Mossy Fibers, Hippocampal / Q000473:pathology; D009474:Neurons / Q000473:pathology*; D017966:Pyramidal Cells / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D016622:Silver Staining; D013550:Swimming; D013569:Synapses / Q000473:pathology*