In Vivo Electrophysiological Recording Techniques for the Study of Neuropathic Pain in Rodent Models

Fei‐Yue Zhao1, Ross Jeggo1, Haifeng Wei1, Andrew Whyment1, Xin Fang1, David Spanswick2

1 NeuroSolutions Limited, Coventry, 2 Warwick Medical School, University of Warwick, Coventry
Publication Name:  Current Protocols in Pharmacology
Unit Number:  Unit 11.15
DOI:  10.1002/0471141755.ph1115s66
Online Posting Date:  September, 2014
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Abstract

Neuropathic pain develops following nerve injury, and is a chronic pain syndrome that can persist long after repair of a wound or removal of the neurological insult. This condition remains poorly treated, not least because of a lack of mechanism‐based therapeutics. Clinically, neuropathic pain is characterized by three major symptoms: thermal or mechanical allodynia (pain sensation in response to previously non‐noxious stimuli); hyperalgesia (enhanced pain sensation to noxious stimulation); and spontaneous, ongoing pain. These clinical symptoms can be modeled in rodent neuropathic pain models using behavioral and electrophysiological readouts. This unit describes techniques designed to record pathophysiological electrical activity associated with neuropathic pain at the level of the periphery, in single fibers of primary sensory neurons, and from wide dynamic range (WDR) neurons of the dorsal horn of the spinal cord. These techniques can be employed in both naïve animals and in animal models of neuropathy to investigate fundamental mechanisms contributing to the neuropathic pain state and the site, mode, and mechanism of action of putative analgesics. Curr. Protoc. Pharmacol. 66:11.15.1‐11.15.26. © 2014 by John Wiley & Sons, Inc.

Keywords: electrophysiology; peripheral nerve; ectopic discharge; spinal cord; dorsal horn neurons; neuropathic pain

     
 
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Table of Contents

  • Introduction
  • Basic Protocol 1: Measurement and Characterization of Spontaneous Ectopic Discharge Recorded From Peripheral Nerve Bundles of the Sciatic Nerve in Neuropathic Model Rats
  • Basic Protocol 2: Measurement of Spontaneous, Wind‐Up, and After‐Discharge Activity of Wide‐Dynamic‐Range Dorsal Horn Neurons, Recorded from the Spinal Cord of Neuropathic Model Rats
  • Alternate Protocol 1: Recording Ectopic Discharge from Modified Preparations of Neuropathic Animals
  • Alternate Protocol 2: Recording WDR Neuron Activity from Modified Preparations of Neuropathic Animals
  • Reagents and Solutions
  • Commentary
  • Literature Cited
  • Figures
     
 
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Materials

Basic Protocol 1: Measurement and Characterization of Spontaneous Ectopic Discharge Recorded From Peripheral Nerve Bundles of the Sciatic Nerve in Neuropathic Model Rats

  Materials
  • Sprague‐Dawley rat (male, 300 to 400 g; neuropathic pain state behaviorally validated, see Commentary; also see unit 5.32)
  • 12% urethane (see recipe)
  • Normal saline (NS, see recipe)
  • Heparinized normal saline (see recipe)
  • Superglue
  • Mineral oil
  • Test substances, e.g., lidocaine, mexiletine, or gabapentin (see recipes)
  • Pentobarbital sodium (see recipe)
  • Syringe pump (Harvard Apparatus; optional)
  • Animal clippers
  • Homeothermic blanket system and rectal probe (Harvard Apparatus)
  • Polyethylene tubing (external/internal diameter 0.96/0.58 mm) for cannulation of jugular vein/carotid artery
  • 26‐G needles
  • Three‐way tap
  • Recommended surgical instruments:
    • Scalpel no. 3 with blade no. 10 or no. 11
    • Hemostatic clamp, curved
    • 15‐cm large operating scissors
    • 8‐cm medium dissection scissors
    • Large blunt‐head dissection forceps, curved
    • Small blunt dissection forceps, curved
    • Fine forceps (No. 5 or 55; two are required)
    • Small arterial clip (micro clamp)
    • Iris scissors, 5.7 cm, curved
    • Suture needles (size 0 and 1)
    • Needle holder
    • Silk suture (4/0 or 3/0)
    • Bone rongeur with extra‐fine tips (Friedman‐Pearson via FST)
  • Hemostatic gelatin sponge
  • Absorbent cotton wool balls
  • Pressure amplifier and transducer (Digitimer, cat. nos. NL108 and NL108T2)
  • Analog/digital converter (Micro1401, Cambridge Electronic Design)
  • Computer running Spike2 software (Cambridge Electronic Design)
  • NeuroLog modular acquisition hardware (NeuroLog, Digitimer, cat. no. NL905)
  • A.C. preamplifier and filter modules (Digitimer, cat. nos. NL104 and NL125)
  • Metal O‐ring frame (6 cm diameter)
  • Stereomicroscope
  • Fiber‐optic light source
  • Opaque plastic platform (∼5 mm × 10 mm)
  • Temper‐annealed silver wire (Ø, 0.37 mm, Advent Research Materials Ltd., cat. no. AG549711)
  • Headstage (Digitimer, cat. no. NL100AK)
  • von Frey hairs (1 g, 4 g, and 15 g; Stoelting, cat. no. 58011)
  • Isolated constant‐voltage stimulator (DS2A, Digitimer)
  • 25‐G syringe needles (Becton Dickinson, cat. no. 300600) connected via insulated copper wires to 4 mm plugs
  • Additional reagents and equipment for injection of rats (Donovan and Brown, )

Basic Protocol 2: Measurement of Spontaneous, Wind‐Up, and After‐Discharge Activity of Wide‐Dynamic‐Range Dorsal Horn Neurons, Recorded from the Spinal Cord of Neuropathic Model Rats

  Materials
  • Test substances, e.g., gabapentin, MK801, or morphine (see recipes)
  • Vibration isolation table with Faraday cage (TMC, Series 20)
  • Stereotaxic frame with two metal spinal cord clamp sets (ST‐7; Narishige)
  • Single‐barrel carbon‐fiber microelectrode (Carbostar‐1, Kation Scientific)
  • Hydraulic single‐axis micromanipulator (MHW‐4, Narishige)
  • Additional reagents and equipment for monitoring ectopic discharge recorded from nerve filaments of anesthetized rats ( protocol 1)

Alternate Protocol 1: Recording Ectopic Discharge from Modified Preparations of Neuropathic Animals

  Additional Materials protocol 11 and protocol 22)
  • Stereotaxic frame with two spinal cord clamps (ST‐7; Narishige)
  • Acetate film strip (cut to approx. 1.5 × 20 cm)
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Figures

Videos

Literature Cited

Literature Cited
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