Effects of high-frequency alternating current on axonal conduction through the vagus nerve

Abstract

High-frequency alternating current (HFAC) is known to disrupt axonal conduction in peripheral nerves, and HFAC has much potential as a therapeutic approach for a number of pathological conditions. Many previous studies have utilized motor output as a bioassay of effects of HFAC on conduction through medium- to large-diameter motor axons. However, little is known about the effectiveness of HFAC on smaller, more slowly conducting nerve fibres. The present study tested whether HFAC influences axonal conduction through sub-diaphragmatic levels of the rat vagus nerve, which consists almost entirely of small calibre axons. Using an isolated nerve preparation, we tested the effects of HFAC on electrically evoked compound action potentials (CAPs). We found that delivery of charge-balanced HFAC at 5000 Hz for 1 min was effective in producing reversible blockade of axonal conduction. Both Aδ and C components of the vagus CAP were attenuated, and the degree of blockade as well as time to recovery was proportional to the amount of HFAC current delivered. The Aδ waves were more sensitive than C waves to HFAC blockade, but they required more time to recover.

Conduction block of mammalian myelinated nerve by local cooling to 15–30°C after a brief heating

“…However, this challenge can be met by either enclosing the nerve with two Peltier devices or by covering the nerve with a highly thermal conductive metal on a Peltier device. Therefore, if a thermal block technology based on this study can be proven in the future to be safe and effective in human subjects, it could potentially be used for many clinical applications to treat chronic disorders such as obesity, pain, heart failure, and voiding dysfunction after spinal cord injury (Ceullar et al 2013; Floras 2009;Gaunt and Prochazka 2009;Sarr et al 2012;Tai et al 2004;van Buyten et al 2013;Waataja et al 2011). It is worth noting that this study only investigated the block of motor nerves.…”

“…Therefore, clinical application of cold/heat block to treat chronic disorders currently remains elusive. If a thermal block of nerve conduction is practically achievable, it will have a wide range of clinical applications to treat many chronic disorders, for example, blocking the abdominal vagus nerve to treat obesity (Sarr et al 2012;Waataja et al 2011), blocking sensory axons in the dorsal roots to treat chronic pain of peripheral origin (Cuellar et al 2013;van Buyten et al 2013), blocking sympathetic nerves to treat heart failure (Floras 2009), and blocking the pudendal nerve to induce efficient voiding after spinal cord injury (Gaunt and Prochazka 2009).…”

Reversible Conduction Block in Peripheral Nerve Using Electrical Waveforms

“…Even after the KHFAC is stopped, there is a continuation of the depression in nerve conduction. Waataja et al [17] showed this effect after only 1 min of KHFAC delivery in the vagal nerve of the rat. This is in contrast to experiments in the rat and cat sciatic nerves, where immediate reversibility can be maintained for at least 40 min [18].…”

Effects of chronic abdominal vagal stimulation of small-diameter neurons on brain metabolism and food intake

“…High frequency alternating current (HFAC) of approximately 5 kHz is known to inhibit action potentials (36) and has been used on the vagus nerve to improve weight control in obese individuals (37). While the therapeutic success of the latter is still to be proven (3), the differences between the two strategies encompassed (i) the duty cycle 25/50 vs 50/50, (ii) the pulse frequency 13 vs 5 kHz, (iii) the current amplitude 15 mA vs 6 mA, positive pulses follow by passive discharge for our strategy vs pure alternative pulses for the VBLOC solution.…”