2007 Fiscal Year Final Research Report Summary
Studies of local anesthetics on use-dependent block
| Project/Area Number |
18591711
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Anesthesiology/Resuscitation studies
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| Research Institution | University of Miyazaki |
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Principal Investigator |
TAKASAKI Mayumi University of Miyazaki, Director (30094212)
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| Co-Investigator(Kenkyū-buntansha) |
TANIGUCHI Masahiko University of Miyazaki, Faculty of Medicine, Intensive Care Unit, Assistant Professor (70305085)
TATEYAMA Shingo University of Miyazaki, Faculty of Medicine, Department of Anesthesiology & Intensive Care, Instructor (10372799)
IBUSUKI Shoichiro University of Miyazaki, Faculty of Medicine, Surgical Division, Assistant Professor (70315381)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Local anesthetics / Use-dependent block / Intracellular concentration |
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| Research Abstract |
Clinically, lidocaine requires a large concentration than bupivacaine to block nerves. Local anesthetics access to sodium channels from the intracellular milieu. Primarily, we determined the intracellular concentrations of lidocaine and bupivacaine when a nerve was blocked in the giant axon of a crayfish. A solution of lidocaine or bupivacaine was perfused, and a nerve block was determined as the absence of an evoked action potential after tonic or phasic electrical stimulation. The intracellular lidocaine or bupivacaine concentration was measured using a lidocaine- or bupivacaine-sensitive glass microelectrode. A phasic block was more effectively and rapidly achieved with a smaller concentration of bupivacaine than with lidocaine. An 11 to 16-fold larger intracellular concentration of lidocaine than bupivacaine was observed to block a single nerve. The ratio of the intra-to extracellular concentration was significantly larger for lidocaine than for bupivacaine. These findings suggest that bupivacaine produces a more potent nerve block and a use-dependent (phasic) block at smaller concentrations than lidocaine. Secondarily, we determined the intracellular concentration of licocaine when a nerve was blocked with lidocaine alone or dimethylsulfoxide (DMSO)-containing lidocaine. The giant axon of crayfish was blocked dose-dependently with DMSO but not blocked with 0.2%DMSO. However, 0.2%DMSO-containing lidocaine produced significantly greater block than lidocaine alone. The intra- to extracellular ratio of lidocaine was similar in the 0.2%DMSO-containing lidocaine and lidocaine alone. These results demonstrate that nerve conduction block is modified by other mechanism except blocking effect of sodium channel from the axoplasma.
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