Document Detail

Barbiturates: active form and site of action at node of Ranvier sodium channels.
MedLine Citation:
PMID:  6264067     Owner:  NLM     Status:  MEDLINE    
Barbiturate sodium channel block was investigated in the voltage-clamped amphibian node of Ranvier. Internal pH was manipulated by diffusion of buffers from the cut internodes. Like local anesthetics and volatile general anesthetics, barbiturates shift the voltage dependence of inactivation in the hyperpolarizing direction. A barbiturate anion, 5-phenyl barbituric acid, blocks sodium channels when applied externally or internally. On external application, block is of very slow onset. The barbiturate anion, like the local anesthetic cation, thus appears to bind to a receptor site on the axoplasmic side of the membrane. Unlike local anesthetics, however, phenobarbital exerts a frequency-dependent block which is modified by changes in internal pH and is not affected by changes in external pH. In addition, barbiturate frequency dependence is apparently more exclusively involved with channel inactivation. The results suggest a barbiturate sodium channel binding site closer to the axoplasm than the local anesthetic binding site is and also suggest that there is a proton barrier between the two sites.
J J Kendig
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of pharmacology and experimental therapeutics     Volume:  218     ISSN:  0022-3565     ISO Abbreviation:  J. Pharmacol. Exp. Ther.     Publication Date:  1981 Jul 
Date Detail:
Created Date:  1981-08-27     Completed Date:  1981-08-27     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0376362     Medline TA:  J Pharmacol Exp Ther     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  175-81     Citation Subset:  IM    
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MeSH Terms
Anions / pharmacology
Axons / metabolism
Barbiturates / pharmacology*
Binding Sites
Hydrogen-Ion Concentration
Ion Channels / drug effects*
Lidocaine / pharmacology
Phenobarbital / pharmacology
Rana catesbeiana
Ranvier's Nodes / drug effects*,  metabolism
Sodium / metabolism*
Xenopus laevis
Grant Support
Reg. No./Substance:
0/Anions; 0/Barbiturates; 0/Ion Channels; 137-58-6/Lidocaine; 50-06-6/Phenobarbital; 7440-23-5/Sodium

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

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