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Canadian Journal of Anesthesia

, Volume 46, Issue 12, pp 1156–1163 | Cite as

Intra-axonal continuous measurement of lidocaine concentration and pH in squid giant axon

  • Shigeru Sano
  • Satoshi Yokono
  • Hiroyuki Kinoshita
  • Kenji Ogli
  • Hiromu Satake
  • Takuo Kageyama
  • Shoji Kaneshina
Laboratory Investigations

Abstract

Purpose

To measure the dynamic penetration process of lidocaine, lidocaine concentration (Ci) and pH (pHi) in squid giant axon, and to determine the times and Ci of disappearance and reappearance of action potentials (AP).

Methods

Lidocaine solutions adjusted to four different pHs (pH = 5.5, 6.8, 7.8 and 9.0) were externally administered to the axon and Ci and pHi were measured using lidocaine and pH microsensors. The times and Ci when the AP just disappeared and reappeared were recorded. In addition, for comparison with Ci, the lidocaine content in the whole axon (Cw) was measured with high-performance liquid chromatography (HPLC).

Results

The Ci (charged plus uncharged) was 1.5 times greater than the uncharged form of administered lidocaine. The changes in pHi depended on the increase in Ci. The AP disappeared only after administration of high pH lidocaine solutions (pH = 7.8, 9.0) and reappeared by washing out the solution in the chamber. Nerve block occurred more rapidly at pH 9.0 than at pH 7.8, and the time after washing out the lidocaine was longer at pH 9.0 than at pH 7.8. The mean Ci and charged lidocaine concentration in the axoplasm, when the AP disappeared or reappeared, were lower at pH 9.0 than at pH 7.8 (P < 0.05).

Conclusion

Uncharged lidocaine penetrates the axon membrane to the axoplasm where it changes to the charged form and is concentrated in the axon membrane and axoplasm. External application of uncharged lidocaine plays a role in modulating nerve conduction.

Keywords

Lidocaine Nerve Conduction Charged Form Giant Axon Axon Membrane 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Résumé

Objectif

Mesurer le processus de pénétration dynamique de la lidocaïne, la concentration de lidocaïne (Ci) et le pH (pHi) dans un axone géant de calmar et déterminer les temps et la Ci de disparition et de réapparition des potentiels d’action (PA).

Méthode

Les solutions de lidocaïne, préparées selon quatre pH différents (pH = 5,5; 6,8; 7,8 et 9,0), ont été administrées sur la paroi externe de l’axone et la Ci et le pHi ont été mesurés en utilisant de la lidocaïne et des microdétecteurs de pH. Les temps et les Ci correspondants au moment de disparition et de réapparition du PA ont été enregistrés. De plus, pour comparer avec la Ci, le contenu de lidocaïne de l’axone complet (Cc) a été mesuré par Chromatographie liquide à haute pression (CLHP).

Résultats

La Ci (ionisée plus non ionisée) a été 1,5 fois plus élevée que la forme non ionisée de lidocaïne administrée. Les changements de pHi dépendaient de l’augmentation de Ci. Le PA a disparu seulement après l’administration de solutions de lidocaïne à pH élevé (pH = 7,8; 9,0) et a réapparu quand on a rincé la solution dans la cuve. Le blocage nerveux est survenu plus rapidement sous un pH de 9,0 que sous un pH de 7,8 et le temps après le rinçage de la lidocaïne a été plus long sous un pH de 9,0 que sous un pH de 7,8. La Ci moyenne et la concentration de lidocaïne ionisée dans l’axoplasme, au moment où le PA disparaissait ou réapparaissait, ont été plus faibles sous un pH de 9,0 que sous un pH de 7,8 (P < 0,05).

Conclusion

La lidocaïne non ionisée pénètre la membrane axonale jusqu’à l’axoplasme où elle se transforme en lidocaïne ionisée et est concentrée dans la membrane axonale et l’axoplasme. L’application externe de lidocaïne non ionisée joue un rôle en modulant la conduction nerveuse.

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Copyright information

© Canadian Anesthesiologists 1999

Authors and Affiliations

  • Shigeru Sano
    • 4
  • Satoshi Yokono
    • 4
  • Hiroyuki Kinoshita
    • 1
  • Kenji Ogli
    • 4
  • Hiromu Satake
    • 2
  • Takuo Kageyama
    • 3
  • Shoji Kaneshina
    • 3
  1. 1.Department of AnesthesiologyAsa Municipal HospitalHiroshima
  2. 2.Institute for Cooperative ResearchUniversity of TokushimaTokushimaJapan
  3. 3.Department of Biological Science and TechnologyUniversity of TokushimaTokushimaJapan
  4. 4.Department of Anesthesiology and Emergency MedicineKagawa Medical UniversityKagawaJapan

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