Transcutaneous electrical nerve stimulation (TENS) reduces chronic hyperalgesia induced by muscle inflammation

Abstract

Transcutaneous electrical nerve stimulation (TENS) reduces pain through central mechanisms involving spinal cord and brainstem sites. Since TENS acts through central mechanisms, we hypothesized that TENS will reduce chronic bilateral hyperalgesia produced by unilateral inflammation when applied either ipsilateral or contralateral to the site of muscle inflammation. Sprague-Dawley rats were injected with carrageenan in the left gastrocnemius muscle belly. Mechanical withdrawal threshold was tested bilaterally before and 2 weeks after carrageenan injection. After testing withdrawal thresholds at 2 weeks, rats received TENS treatment either ipsilateral or contralateral to the site of inflammation. In each of these groups, rats were randomized to control (no TENS), low frequency (4 Hz), or high frequency (100 Hz) TENS treatment. TENS was applied for 20 min at sensory intensity under light halothane anesthesia. Mechanical withdrawal thresholds were re-assessed after TENS or 'no TENS' treatment. Unilateral injection of carrageenan to the gastrocnemius muscle significantly reduced the mechanical withdrawal threshold (mechanical hyperalgesia) bilaterally 2 weeks later. Either low or high frequency TENS applied to the gastrocnemius muscle ipsilateral to the site of inflammation significantly reversed mechanical hyperalgesia, both ipsilateral and contralateral to the site of inflammation. Low or high frequency TENS applied to the gastrocnemius muscle contralateral to the site of inflammation also significantly reduced mechanical hyperalgesia, both ipsilateral and contralateral to the site of inflammation. Since ipsilateral or contralateral TENS treatments were effective in reducing chronic bilateral hyperalgesia in this animal model, we suggest that TENS act through modulating descending influences from supraspinal sites such as rostral ventromedial medulla (RVM).

Antinociceptive action of botulinum toxin type A in carrageenan-induced mirror pain

“…carrageenan is assumed to be centrally mediated as well, since the myositis occurs on ipsilateral side only (Radhakrishnan et al 2003). Additionally, gastrocnemius transcutaneous electric nerve stimulation (TENS) alleviates bilateral pain independently of side of application (Ainsworth et al 2006). This effect is assumed to be mediated through RVM modulation Desantana et al 2009).…”

Mild Electrical Stimulation Increases Ubiquitinated Proteins and Hsp72 in A549 Cells via Attenuation of Proteasomal Degradation

“…Positive medical effects of applied low electric current, such as decreased inflammation, bone fracture healing, and alleviation of pain, have been reported (2,3). It is hypothesized that the therapeutic effects of applied low electrical field strength are due to enhanced signal transduction (4), a hypothesis that was partly validated by a study demonstrating that electrical signals activate the phosphatidylinositol-3-OH kinase (PI-3 kinase) and promote wound healing (5).…”

An animal model of functional electrical stimulation: evidence that the central nervous system modulates the consequences of training

“…9,21 Continuous electrical stimulation through fixed skin electrodes is often used in clinical settings to induce a pain-inhibitory effect, a procedure known as transcutaneous electrical nerve stimulation (TENS). 22 If intermittent shock impairs spinal plasticity, because it overexcites nociceptive systems, perhaps the induction of the opposite phenomenon (antinociception) would have a protective effect. Supporting this, Crown et al 10 applied a continuous shock to the tail, whereas spinal rats received intermittent shock (180 80-ms shocks, presented approximately 2 s apart) to one hind leg.…”