original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
Both transcutaneous electrical nerve stimulation (TENS) and morphine are commonly used for relief of pain. Extensive research has been done on the effectiveness of each of these two methods for pain relief when given independently. However, very little literature exists examining the effectiveness of their combined use. Systemically administered morphine activates mu opioid receptors and when administered for prolonged periods results in analgesic tolerance. Low (4 Hz) and high (100 Hz) frequency TENS activate mu- and delta-opioid receptors, respectively, It is thus possible that TENS would be less effective in morphine-tolerant subjects. The current study investigated the effectiveness of high- and low-frequency TENS in the reversal of hyperalgesia in inflamed rats that were morphine-tolerant. Morphine tolerance was induced by subcutaneous implantation of morphine pellets over 10 days. Knee joint inflammation was induced by injection of kaolin and carrageenan into the knee joint cavity. Secondary heat hyperalgesia was tested by measuring the paw withdrawal latency to radiant heat (1) before pellet implantation (either morphine or placebo), (2) after pellet implantation and before inflammation, (3) after inflammation and (4) after TENS. Both high (100 Hz) and low (4 Hz) frequency TENS caused nearly 100% inhibition of secondary hyperalgesia in animals receiving placebo pellets. In contrast, the hyperalgesia in morphine-tolerant animals with knee joint inflammation was unaffected by low frequency TENS but fully reversed by high frequency TENS. These results suggest that patients who are tolerant to morphine may respond better to high frequency TENS than to low frequency TENS.
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
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- Modulation in the elastic properties of gastrocnemius muscle heads in individuals with plantar fasciitis and its relationship with pain. Zhou 2020 Sci Rep.
- Association Between Plantar Fasciitis and Isolated Gastrocnemius Tightness. Nakale 2018 Foot Ankle Int.
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- The neck and headaches. Bogduk 2014 Neurol Clin.