Linked Life Data

7690845

Source:http://linkedlifedata.com/resource/pubmed/id/7690845

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1993-10-21
pubmed:abstractText
During K(+)-induced depolarization of isolated rat brain nerve terminals (synaptosomes), 1 mM Ba2+ could substitute for 1 mM Ca2+ in evoking the release of endogenous glutamate. In addition, Ba2+ was found to evoke glutamate release in the absence of K(+)-induced depolarization. Ba2+ (1-10 mM) depolarized synaptosomes, as measured by voltage-sensitive dye fluorescence and [3H]-tetraphenylphosphonium cation distribution. Ba2+ partially inhibited the increase in synaptosomal K+ efflux produced by depolarization, as reflected by the redistribution of radiolabeled 86Rb+. The release evoked by Ba2+ was inhibited by tetrodotoxin (TTX). Using the divalent cation indicator fura-2, cytosolic [Ca2+] increased during stimulation by approximately 200 nM, but cytosolic [Ba2+] increased by more than 1 microM. Taken together, our results indicate that Ba2+ initially depolarizes synaptosomes most likely by blocking a K+ channel, which then activates TTX-sensitive Na+ channels, causing further depolarization, and finally enters synaptosomes through voltage-sensitive Ca2+ channels to evoke neurotransmitter release directly. Though Ba(2+)-evoked glutamate release was comparable in level to that obtained with K(+)-induced depolarization in the presence of Ca2+, the apparent intrasynaptosomal level of Ba2+ required for a given amount of glutamate release was found to be several-fold higher than that required of Ca2+.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0022-3042
pubmed:author
pubmed:issnType
Print
pubmed:volume
61
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1220-30
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1993
pubmed:articleTitle
Barium evokes glutamate release from rat brain synaptosomes by membrane depolarization: involvement of K+, Na+, and Ca2+ channels.
pubmed:affiliation
Department of Pharmacology, Medical College of Pennsylvania, Philadelphia, Pennsylvania 19129.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't