An Ultrasonic Tool for Nerve Conduction Block in Diabetic Rat Models

Summary

This work presents the methodology of applying high intensity-focused ultrasound to block the action potentials of diabetic neuropathic nerves.

Abstract

Nerve conduction block with a high intensity-focused ultrasound (HIFU) transducer has been performed in normal and diabetic animal models recently. HIFU can reversibly block the conduction of peripheral nerves without damaging the nerves while using an appropriate ultrasonic parameter. Temporary and partial block of the action potentials of nerves shows that HIFU has the potential to be a useful clinical treatment for pain relief. This work demonstrates the procedures for suppressing the action potentials of neuropathic nerves in diabetic rats in vivo using an HIFU transducer. The first step is to generate adult male diabetic neuropathic rats by streptozotocin (STZ) injection. The second step is to evaluate the peripheral diabetic neuropathy in STZ-induced diabetic rats by an electronic von Frey probe and a hot plate. The final step is to record in vivo extracellular action potentials of the nerve exposed to HIFU sonication. The method showed here may benefit the study of ultrasound analgesic applications.

Introduction

Oral medications, acupuncture¹, and electrical nerve stimulation² have been used for the treatment of painful diabetic polyneuropathy. However, the side effects of the oral medications, invasive operation of acupuncture, and electrical nerve stimulation hamper the therapeutic efficacy and patient's adherence. Ultrasound block of peripheral nerves in animal models has been investigated for decades^3,4,5. The conduction of in vitro sciatic nerves of the large green frog was inhibited reversibly after the treatment of 1....

Protocol

The Institutional Animal Care and Use Committee of the National Health Research Institutes in Taiwan approved all animal protocols.

1. Induction of Diabetic Model in Male Adult Sprague - Dawley (SD) Rats

1. Remove rat food pellets from the cage to fast male SD rats (300 - 350 g) for 6 h prior to STZ induction.
2. Prepare sodium citrate buffer (0.1 M, pH 4.5).
   1. Dissolve 1.05 g citric acid monohydrate (C₆H₈O₇ · H₂O; mol. wt. 210.14) in 50 mL distilled water to make a 0.1 M citric acid solution.
   2. Dissolve 1.47 g trisodium citrate dihydrate (C₈H

Results

The in vivo study demonstrated that, with an HIFU dose of 3 s sonication at an intensity of 2,810 W/cm², the CMAPs were suppressed by 20% of baseline, but they were completely recovered after 30 min (Figure 2A, diamonds) and were almost constant in the period of 28 days (Figure 2B, diamonds). For the 5 s HIFU exposure at the same intensity, the CMAPs decreased to 65.4% (9.5%) of baseline at 4 min and recovered.......

Discussion

Partial and temporary suppression of action potentials of the neuropathic nerves from diabetic rats in vivo and instant occurrence of the blocking effect after HIFU treatment both were observed. The 28-day follow-up study on CMAPs demonstrated that a safe blockade of the nerve conduction could be carried out at an appropriate HIFU exposure. As a result, the above protocol of the HIFU treatment can provide an alternative solution for the reversible conduction block of sciatic nerves in diabetic rats.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
streptozotocin	Sigma	85882
citric acid monohydrate	Sigma	C1909
trisodium citrate dihydrate	Sigma	W302600
glucose meters	Roche Accu-Check Active	GC
electronic von Frey device	IITC Life Science	2390
hot plate	IITC Life Science
Biopac MP36 acquisition system	Biopac Systems, Inc.
HIFU transducer	Sonic Concepts	H108
function generator	Agilent	33250A
power amplifier	Electronics & Innovation	1040L
Rats	Biolasco taiwan	Sprague-Dawley
Puralube vet ointment	Dechra
isoflurane vaporizer	Parkland Scientific	V3000PS
Isoflurance	Attane
Restraint bag (Decapicones)	Braintree Scientific	DC 200