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Local anesthetic action of carboxylic esters: evidence for the significance of molecular volume and for the number of sites involved
journal contribution
posted on 2023-06-08, 19:54 authored by J R Elliott, Ruth Murrell-LagnadoRuth Murrell-Lagnado, D A HaydonThe effects of the homologous series of carboxylic esters, methyl propionate to methyl decanoate, on the steady-state inactivation of the sodium current in squid axons have been studied. The esters moved the relationship between the inactivation parameter, h infinity, and the membrane potential in the hyperpolarizing direction, thus reducing the number of sodium channels available at the resting potential. The concentration dependence of the shift at the mid-point of the curve of h infinity against potential has been measured for all esters except decanoate, which was almost inactive. Two aspects of these concentration dependences suggest that molecular volume is an important determinant of the effectiveness of each ester. Firstly, there is a sharp decline in activity above methyl hexanoate. This cut-off in activity resembles that for hydrocarbons where it has been suggested [e.g., Haydon, D.A., Urban, B.W. 1983, J. Physiol. (London) 341:411-427] to a result from a decrease in uptake with increasing molecular volume. (Further data for the hydrocarbons n-butane to n-heptane are reported here.) Secondly, the smallest compounds, methyl propionate and methyl butyrate, are less effective than would be predicted if equal membrane concentrations of each ester produced the same shift. The aqueous concentration dependences for these esters indicate that below methyl hexanoate, as the series is descended, progressively higher membrane concentrations are required to produce a given shift. This would be expected if the volume of ester in the membrane, rather than the number of molecules, is important.(ABSTRACT TRUNCATED AT 250 WORDS)
History
Publication status
- Published
Journal
Journal of Membrane BiologyISSN
0022-2631Publisher
Springer VerlagExternal DOI
Issue
2Volume
95Page range
143-149Department affiliated with
- Biochemistry Publications
Full text available
- No
Peer reviewed?
- Yes
Legacy Posted Date
2015-03-25Usage metrics
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