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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
8
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pubmed:dateCreated |
1992-9-4
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pubmed:abstractText |
This study analyzes the synaptic interactions between the central terminals of A delta high threshold mechanoreceptors (A delta HTMs) and GABA-immunoreactive profiles. A delta HTM primary afferents from three monkeys and one cat were electrophysiologically identified and intracellularly labeled with HRP, and their terminal arborizations in laminae I and II of the sacrocaudal spinal cord were studied at the ultrastructural level. GABA-immunoreactive profiles in relation to A delta HTM terminals were demonstrated using postembedding colloidal gold techniques. Monkey A delta HTM terminals (n = 131) usually constituted the central element of synaptic glomeruli; they established large asymmetric synaptic contacts with 1-13 dendrites (modal value 2-4) and were surrounded by 0-6 peripheral axon terminals (modal value 2-3). The large majority (around 85%) of the peripheral axon terminals were GABA immunoreactive. They were found presynaptic to the A delta HTM terminal and/or to dendrites postsynaptic to the primary afferent terminal. Furthermore, all peripheral axon terminals found presynaptic to the A delta HTM terminals showed GABA immunoreactivity. Within a single A delta HTM fiber, this synaptic arrangement was found in 20-60% of its boutons. In addition, 28% of the postsynaptic dendritic profiles displayed weak GABA immunoreactivity. Some of them contained vesicles; however, only in a few cases did we observe synapses between a GABA-immunoreactive vesicle-containing dendrite and a dendritic profile postsynaptic to an A delta HTM terminal. Similar synaptology and interactions with GABA-immunoreactive profiles were displayed by the terminals of the single cat A delta HTM fiber studied. Our data support the hypothesis that GABA-containing neurons use both presynaptic and/or postsynaptic mechanisms to exert a powerful control, presumably inhibitory, over the transmission of nociceptive information between A delta HTM afferents and second-order neurons in monkey and cat spinal cord. Our results also imply that GABA may be released within the synaptic glomeruli formed by A delta HTM terminals either by local dendrites or by axon terminals. We discuss the possibility that these GABAergic synapses can be driven by inputs from both primary afferents and/or descending systems to modulate the transmission of nociceptive sensory information.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical | |
pubmed:status |
MEDLINE
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pubmed:month |
Aug
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pubmed:issn |
0270-6474
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
12
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
2901-17
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:1494939-Animals,
pubmed-meshheading:1494939-Cats,
pubmed-meshheading:1494939-Macaca mulatta,
pubmed-meshheading:1494939-Nerve Endings,
pubmed-meshheading:1494939-Nerve Fibers, Myelinated,
pubmed-meshheading:1494939-Nociceptors,
pubmed-meshheading:1494939-Spinal Cord,
pubmed-meshheading:1494939-Synapses,
pubmed-meshheading:1494939-gamma-Aminobutyric Acid
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pubmed:year |
1992
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pubmed:articleTitle |
Synaptic interactions between GABA-immunoreactive profiles and the terminals of functionally defined myelinated nociceptors in the monkey and cat spinal cord.
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pubmed:affiliation |
Department of Physiology, School of Medicine, University of North Carolina, Chapel Hill 27599.
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pubmed:publicationType |
Journal Article,
Comparative Study,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
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