PARMACODYNAMIC ANALYSIS OF THE EFFECTS OF LOCAL ANESTHETICS ON THE AXONAL MEMBRANE

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04454389
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: 麻酔学
• Research Institution: KAGAWA MEDICAS SCHOOL
• Principal Investigator: OGILI Kenji KAGAWA MEDICAL SCHOOL・ANESHTESIOLOGY AND ACUTE MEDICINE・PROFESSOR, 医学部, 教授 (40079934)
• Co-Investigator(Kenkyū-buntansha): KINOSHITA Hiroyuki ANESHTESIOLOGY AND ACUTE MEDICINE・ASSOCIATE PROFESSOR, 医学部, 助教授 (60136083) ; YOKONO Satoshi KAGAWA MEDICAL SCHOOL HOSPITAL・ASSOCIATE PROFESSOR, 医学部・附属病院, 助教授 (70106425) ; OOKAWA Kazuaki OSAKA UNIV・FACULTY OF HUMAN SCINECE・ASSISTANT PROFESSOR, 教養部, 助手 (30029714)
• Project Period (FY): 1992 – 1993
• Keywords: Squid giant axon / Local anesthetics / Action Potential / Anesthetic mechanism / Lidocaine senser / Sodium channel / Lipid membrane

Research Abstract

1.Development of microelectrodes : We developed a lidocaine sensitive microelectrode, which is consist of thin copper wire and PVC matrix containing with lidocaine, dioctylphtalate and tetrahydrofuran. The final diameter of the lidocaine microelectrode was 150-200 micrometer. The concentrations of ionized lidocaine were measured by recording the potentials between the microelectorde and Ag/AgCl reference electrode. This electrode showed a linear response to lidocaine at the concentration range from 10^<-6> to 10^<-2> mol/L and the detecting limitation was 10^<-8> mol/L.
2.Recording of the action potentials (AP) of squid giant axon : Squid giant axons were mounted in a chamber, which has 0.4ml in volume and 2cm gap between the stimulation electrode and the recording electrode. When an electricalstimulation was applied from outside of the giant axon, an AP was recorded at the latency time of 0.5ms and it means the conduction velocity of 25m/sec same as reported previously. The camber was filled with an artificial sea water containing 600 mmol of NaCL,10 mmol of KCl, 50 mmol of MgCl2,10 mmol of CaCl2 and 10 mmol of HEPES and the pH was corrected to 8.0.
3.In vitro study : When lidocaine was administered at the concentration of 2 x 10^<-2> mol/L (0.5%) into the bathing medium, ionized lidocaine appeared rapidly in the axoplasm and the AP were disappeared when the concentration of lidocaine in the axoplasm was reached to 5x10^<-4> to 3x10^<-3> mol/L.The time course of this phenomenon was less than 10 min. After removal of lidocaine from the bathing medium, the AP appeared in an on-and-off manner and the concentration of lidocaine were 7x10^<-4> to 2x10^<-3> when the APs appeared.