Document Detail


Distribution pattern of inhibitory and excitatory synapses in the dendritic tree of single masseter alpha-motoneurons in the cat.
MedLine Citation:
PMID:  10531539     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Little is known about the differences in the distributions of inhibitory and excitatory synapses in the dendritic tree of single motoneurons in the brainstem and spinal cord. In this study, the distribution of gamma-aminobutyric acid (GABA)-, glycine-, and glutamate-like immunoreactivity in axon terminals on dendrites of cat masseter alpha-motoneurons, stained intracellularly with horseradish peroxidase, was examined by using postembedding immunogold histochemistry in serial ultrathin sections. The dendritic tree was divided into three segments: primary (Pd) and distal (Dd) dendrites and intermediate (Id) dendrites between the two segments. Quantitative analysis of 175, 279, and 105 boutons synapsing on 13 Pd, 54 Id, and 81 Dd, respectively, was performed. Fifty percent of the total number of studied boutons were immunopositive for GABA and/or glycine and 48% for glutamate. Among the former, 27% showed glycine immunoreactivity only and 14% were immunoreactive to both glycine and GABA. The remainder (9%) showed immunoreactivity for GABA only. As few as 3% of the boutons were immunonegative for the three amino acids. Most boutons immunoreactive to inhibitory amino acid(s) contained a mixture of spherical, oval, and flattened synaptic vesicles. Most boutons immunoreactive to excitatory amino acid contained clear, spherical, synaptic vesicles with a few dense-cored vesicles. When comparisons of the inhibitory and excitatory boutons were made between the three dendritic segments, the proportion of the inhibitory to the excitatory boutons was high in the Pd (60% vs. 37%) but somewhat low in the Id (46% vs. 52%) and Dd (44% vs. 53%). The percentage of synaptic covering and packing density of the inhibitory synaptic boutons decreased in the order Pd, Id, and Dd, but this trend was not applicable to the excitatory boutons. The present study provides possible evidence that the spatial distribution patterns of inhibitory and excitatory synapses are different in the dendritic tree of jaw-closing alpha-motoneurons.
Authors:
Y C Bae; T Nakamura; H J Ihn; M H Choi; A Yoshida; M Moritani; S Honma; Y Shigenaga
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of comparative neurology     Volume:  414     ISSN:  0021-9967     ISO Abbreviation:  J. Comp. Neurol.     Publication Date:  1999 Nov 
Date Detail:
Created Date:  1999-12-10     Completed Date:  1999-12-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0406041     Medline TA:  J Comp Neurol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  454-68     Citation Subset:  IM    
Copyright Information:
Copyright 1999 Wiley-Liss, Inc.
Affiliation:
Kyungpook National Unversity School of Dentistry, Taegue 700-422, Korea.
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MeSH Terms
Descriptor/Qualifier:
Animals
Cats / anatomy & histology*
Dendrites / physiology,  ultrastructure*
Excitatory Postsynaptic Potentials / physiology
Glutamic Acid / analysis
Glycine / analysis
Masseter Muscle / innervation*
Microscopy, Electron
Motor Neurons / physiology,  ultrastructure*
Neural Inhibition / physiology
Synapses / physiology,  ultrastructure*
Trigeminal Nuclei / ultrastructure*
gamma-Aminobutyric Acid / analysis
Chemical
Reg. No./Substance:
56-12-2/gamma-Aminobutyric Acid; 56-40-6/Glycine; 56-86-0/Glutamic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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