Journal article
Deep tissue afferents, but not cutaneous afferents, mediate transcutaneous electrical nerve stimulation-Induced antihyperalgesia
The journal of pain, Vol.6(10), pp.673-680
10/2005
DOI: 10.1016/j.jpain.2005.06.001
PMID: 16202960
Abstract
In this study we investigated the involvement of cutaneous versus knee joint afferents in the antihyperalgesia produced by transcutaneous electrical nerve stimulation (TENS) by differentially blocking primary afferents with local anesthetics. Hyperalgesia was induced in rats by inflaming one knee joint with 3% kaolin-carrageenan and assessed by measuring paw withdrawal latency to heat before and 4 hours after injection. Skin surrounding the inflamed knee joint was anesthetized using an anesthetic cream (EMLA). Low (4 Hz) or high (100 Hz) frequency TENS was then applied to the anesthetized skin. In another group, 2% lidocaine gel was injected into the inflamed knee joint, and low or high frequency TENS was applied. Control experiments were done using vehicles. In control and EMLA groups, both low and high frequency TENS completely reversed hyperalgesia. However, injection of lidocaine into the knee joint prevented antihyperalgesia produced by both low and high frequency TENS. Recordings of cord dorsum potentials showed that both low and high frequency TENS at sensory intensity activates only large diameter afferent fibers. Increasing intensity to twice the motor threshold recruits Adelta afferent fibers. Furthermore, application of EMLA cream to the skin reduces the amplitude of the cord dorsum potential by 40% to 70% for both high and low frequency TENS, confirming a loss of large diameter primary afferent input after EMLA is applied to the skin. Thus, inactivation of joint afferents, but not cutaneous afferents, prevents the antihyperalgesia effects of TENS. We conclude that large diameter primary afferent fibers from deep tissue are required and that activation of cutaneous afferents is not sufficient for TENS-induced antihyperalgesia.
Transcutaneous electrical nerve stimulation (TENS) is an accepted clinical modality used for pain relief. It is generally believed that TENS analgesia is caused mainly by cutaneous afferent activation. In this study by differentially blocking cutaneous and deep tissue primary afferents, we show that the activation of large diameter primary afferents from deep somatic tissues, and not cutaneous afferents, are pivotal in causing TENS analgesia.
Details
- Title: Subtitle
- Deep tissue afferents, but not cutaneous afferents, mediate transcutaneous electrical nerve stimulation-Induced antihyperalgesia
- Creators
- Rajan Radhakrishnan - Graduate Program in Physical Therapy and Rehabilitation Science, Pain Research Program, Neuroscience Graduate Program, University of Iowa, Iowa City, Iowa 52242, USAKathleen A Sluka
- Resource Type
- Journal article
- Publication Details
- The journal of pain, Vol.6(10), pp.673-680
- Publisher
- United States
- DOI
- 10.1016/j.jpain.2005.06.001
- PMID
- 16202960
- ISSN
- 1526-5900
- eISSN
- 1528-8447
- Grant note
- K02 AR02201 / NIAMS NIH HHS
- Language
- English
- Date published
- 10/2005
- Academic Unit
- Iowa Neuroscience Institute; Nursing; Physical Therapy and Rehabilitation Science; Neuroscience and Pharmacology
- Record Identifier
- 9984040380202771
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