Document Detail

Sites of action of procaine at the motor end-plate.
MedLine Citation:
PMID:  6308216     Owner:  NLM     Status:  MEDLINE    
The effects of procaine at pH 7.4 and 9.9 were studied by examining the decay phase of spontaneous miniature end-plate currents (m.e.p.c.s) recorded from toad sartorius muscle fibres. Following exposure to procaine (0.05-0.1 mM) at pH 7.4, the decay of m.e.p.c.s rapidly became biphasic, and could be described as the sum of two exponential components. When the same concentrations of procaine were applied at pH 9.9, the development of biphasic m.e.p.c.s took much longer. Reversal of the effect upon washing out the procaine was much slower at pH 9.9 than at pH 7.4. A rapid change in pH from 7.4 to 9.9 during exposure to a constant concentration of procaine quickly reduced the effect of procaine on m.e.p.c.s. The effect gradually returned after prolonged exposure to procaine at pH 9.9. These results suggest that procaine applied at high pH, where it is predominantly in uncharged form, may be diffusing to a site of action which is not directly accessible from the external surface of the membrane. The voltage-dependence of procaine action was similar whether it was applied at pH 7.4 or 9.9. Intracellular injection of procaine rapidly produced biphasic m.e.p.c.s, whether the extracellular pH was 7.4 or 9.9. The effect of membrane potential on these m.e.p.c.s was similar to that seen for biphasic m.e.p.c.s produced by extracellular application of procaine. The results indicate that procaine can affect end-plate channels when applied to either surface of the muscle membrane, and that the voltage-dependence of procaine action does not arise from the influence of membrane field on the movement of charged procaine molecules into open channels.
P W Gage; O P Hamill; R E Wachtel
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of physiology     Volume:  335     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1983 Feb 
Date Detail:
Created Date:  1983-09-23     Completed Date:  1983-09-23     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  123-37     Citation Subset:  IM    
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MeSH Terms
Bufo marinus
Hydrogen-Ion Concentration
Ion Channels / drug effects
Membrane Potentials / drug effects
Motor Endplate / drug effects*,  physiology
Muscles / innervation
Neuromuscular Junction / drug effects*
Procaine / pharmacology*
Time Factors
Reg. No./Substance:
0/Ion Channels; 59-46-1/Procaine

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

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