Modular double sucrose gap apparatus for improved recording of compound action potentials from rat and mouse spinal cord white matter preparations

J Neurosci Methods. 2010 Mar 15;187(1):33-40. doi: 10.1016/j.jneumeth.2009.12.006. Epub 2009 Dec 23.

Abstract

Compound action potential (CAP) recording is a powerful tool for studying the conduction properties and pharmacology of axons in multi-axonal preparations. The sucrose gap technique improves CAP recording by replacing the extracellular solution between the recording electrodes with a non-conductive sucrose solution to minimize extracellular shunting. The double sucrose gap (DSG), conferring similar advantages at the stimulation site, has been extensively used on guinea pig spinal cord white matter (WM) in vitro. Establishing the DSG methodology for WM preparations from smaller animals such as rats and mice is appealing due to their extensive use in basic and translationally oriented research. Here we describe a versatile modular DSG apparatus with rubber membrane separation of the compartments, suitable for WM strips from rat and mouse spinal cord. The small volumes of compartments (<0.1 ml) and the air-tight design allow perfusion rates of 0.5-1 ml/min with faster refreshment rates compared to commonly used 2-3 ml/min and larger compartments, providing economical usage of expensive pharmacological drugs. Our improved DSG design is particularly efficient for uncovering slower conducting, higher threshold CAP components, as demonstrated by recordings of C-wave (non-myelinated axons) in rat dorsal WM. In myelin-deficient Shiverer mice with genetically dysmyelinated axons, our DSG apparatus recordings revealed a multi-peak C-wave without preceding faster components. The improved stimulation and recording with our DSG apparatus, lowering the range of required stimulus intensities and reducing the artifact interference with recorded CAPs provide for critical technical advantages that allow for more detailed analysis of CAPs in relatively short preparations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology*
  • Air
  • Animals
  • Artifacts
  • Cell Hypoxia / physiology
  • Electric Stimulation / instrumentation
  • Electric Stimulation / methods
  • Electrophysiology / instrumentation*
  • Electrophysiology / methods*
  • Extracellular Space
  • Glucose / deficiency
  • Glucose / metabolism
  • In Vitro Techniques
  • Mice
  • Mice, Transgenic
  • Microelectrodes
  • Nerve Fibers, Unmyelinated / drug effects
  • Nerve Fibers, Unmyelinated / physiology
  • Rats
  • Sodium Channel Blockers / pharmacology
  • Spinal Cord / drug effects
  • Spinal Cord / physiology*
  • Sucrose*
  • Tetrodotoxin / pharmacology
  • Time Factors

Substances

  • Sodium Channel Blockers
  • Tetrodotoxin
  • Sucrose
  • Glucose