• The Korean Journal of Physiology
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• v.26 no.2
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• pp.143-150
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• 1992

The purpose of this study is to obtain the effective concentration of capsaicin to relieve pain with no change in the number of C-fibers and its effective duration for pain relief. Capsaicin has been used extremely as a experimental tool and as topical medications for acute or chronic tissue injuries and partial nerve injury is the main cause of causalgiform pain disorders in humans. Here, the left sciatic nerve was ligated unilaterally at the high level of the thigh to prepare an animal model of this pain condition. The rat developed guarding behavior of the ipsilateral hind paw within a few hours after the operation and this behavior was maintained for several months thereafter, suggesting the possibility of spontaneous pain. These animals were divided into two groups(4-week & 8-week) and each group was subdivided into five groups by different concentration (0.05, 0.1, 0.5, 1.0 & 2.0%). Each capsaicin concentration was treated locally on the spinal cord-side of the ligated nerve and the foot withdrawal latency was measured. Thereafter, the dorsal roots of L5 were removed from both sides immediately after in tracardial perfusion for the counting of C-fibers by the histological procedure. There were no significant differences in the foot-withdrawal latency and the number of C-fibers between the left side treated with 0.05% capsaicin and the right side treated with the vehicle. However, latencies of the left sides treated with 0.1, 0.5, and 1.0% capsaicin increased significantly throughout 4-6 weeks with almost no change in the number of C-fibers, and the latencies showed the trends to approach slowly to those of the conditions after operation. The latency of subgroup treated with 2.0% increased by approximate 10% more than that of the right side throughout 8 weeks, and the number of C-fibers decreased by about 30% or more These results suggest that the elevated latency with capsaicin(0.1-1.0%) treatment is due to the inhibition of impulse transmission throughout the primary afferent fiber and the data from 2.0% are due to partial destruction of C-fibers. Therefore, capsaicin concentrations from 0.1% to 1.0% are probably very effective for the treatment of causalgiform pain with almost no destruction of C-fibers.

• The Journal of Korean Physical Therapy
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• v.15 no.2
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• pp.182-195
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• 2003

This study investigated the effects of triamcinolone acetonide by iontophoretic transdermal drug delivery on anti-inflammatory action into the rats and which had carrageenan-induced hyperalgesia and edema in the feet, trauma-induced tissue damage in the thigh. Each group was treated under the fellowing conditions. 1. Group I : Control group 2. Group II : Application of direct current 3. Group III : Application of 0.1$\%$ triamcinolone acetonide solution 4. Group IV : Iontophoresis of 0.1$\%$ triamcinolone acetonide solution The degree of anti-inflammation was evaluated by the paw withdrawal latency, the change in volume of foot the change of paw edema, histological change in rats. 1. In paw withdrawal latency, group IV showed the most significant therapeutic effect than the other groups at 0, 3, 6 and 9 hours(p < 0.001). 2. In paw edema experiment in the foot, group IV showed the most significant effect than group I at 0, 3, 6 and 9 hours. It meant that there was effective anti-inflammatory reaction in group I (p < 0.001). 3. In the light microscopic observation, group IV showed the most significant reduction of haemorrhage, hyperemia and infiltrative inflammation. From the results, the iontophoresis with triamcinolone acetonide is more effective than using each groups. It is one of the effective physical agent which delivered large molecular weight drug into the body. The continuous study is needed for many interesting issues of iontophoretic transdermal drug delivery in new future.

• YAKHAK HOEJI
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• v.43 no.3
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• pp.404-410
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• 1999

Administration of capsaicin produces acute pain and subsequent long-lasting antinociception. The antinociceptive action site of capsaicin is primarily small afferent nerve fibers. However, the effect of capsaicin on the neural activity of dorsal horn neurons are not well understood. The goal of the present experiment was to study the action of capsaicin on activity of dorsal horn neurons using c-fos immunoreactivity in the spinal cord. Intradermal injection of formalin in the hindpaw produced inflammation in the foot pad and increased the number of cells exhibiting Fos-like immunoreactivity (FLI) in the dorsal horn of the spinal cord, suggesting the hyperalgesia because of the apparent inflammation. Intradermal injection of capsaicin prior to formalin injection significantly reduced the number of cells exhibiting FLI induced by formalin and increased the paw-withdrawal latency, suggesting the hypoalgesic effect of capsaicin. Coadministeration with capsaicin of capsazepine and ruthenium red, antagonists of capsaicin receptor reversed the reduction of formalin-induced FLI by capsaicin. he antagonists also partially antagonized the antinociceptive effect of capsaicin in the paw-withdrawal test. These results further suggest that capsaicin reduces prsponses of dorsal horn neurons to the inflammatory nociceptive stimuli in the periphery. Thus, the reduction of FLI subserves the neural mechanisms underlying analgesia produced by capsaicin.