The incidence of chronic pain among the adult Japanese population has been reported to be around 23%. In the majority of cases, the site of chronic pain is located in the musculoskeletal system, such as the lumbar spine, neck and shoulder joint. Based on the pain mechanism, musculoskeletal chronic pain is classified as chronic nociceptive pain, neuropathic pain or mixed pain. Psycho–social factors often affect clinical symptoms in chronic pain cases.
   The first choice of medication for chronic nociceptive pain, resulting from conditions such as inflammation or degeneration of joints or spine, is nonsteroidal anti–inflammatory drugs (NSAIDs). Cox 2 selective inhibitors should be used in cases of long–term use to avoid gastrointestinal problems. Although opioids may be applied in cases in which NSAIDs have no effect, attention should be paid to potential side effects such as nausea and consti-pation, abuse and addiction. Physical therapy including muscle stretching and strengthening is a very important therapeutic modality for chronic noci-ceptive pain. Surgical treatment, such as arthroplasty and spinal fusion, may also be applied in cases in which conservative treatments fail.
   As NSAIDs are not effective for neuropathic pain caused by disorders and diseases of nervous system, pregabalin (Ca²⁺ channel blocker), anti–depressant s and opioids may be applied. Surgery intervention, including laminectomy, discectomy or neurolysis for the purpose of nerve decompres-sion, may be applied in cases in which conservative treatment fail or nerve palsy is observed. For difficult chronic pain cases with psycho–social factors, a multidisciplinary approach including cognitive behavioral therapy should be considered.

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   The sense of light touch is indispensable for environmental exploration,social interaction, and skilled tasks but the underlying mechanisms are largely unknown in mammals. Tactile dysfunction such as neuropathic pain produce allodynia which is grievous pain generated by light touch. This intra ctable phenomenon is induced by neural sensitization after the damage to nervous system. Along with the nervous system mechanisms, mechano transdcution in the tactile end organs play a crucial role to form mechanical allodynia. Thus, the elucidation of touch mystery is great expected matter to develop the effective treatment against mechanical allodynia. Merkel discs are one of the tactile special end organs thought as putative mechanoreceptors in the skins and can make sophisticated discrimination. We performed in situ patch–clamp recording from Merkel cells which compose Merkel discs in company with Aβ–afferent nerve endings. As a result, Merkel cells showed transduction of tactile stimuli via “Piezo2” channels and encode tactile signals in the form of Ca²⁺ action potentials. Recent advances using conditional knock out mice also show the same molecular mechanisms for Merkel cells mechanotransduction. These findings provide new insights into how to achieve delicate tactile sensation and may have clinical therapeutic implications.

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   Physical exercise such as running or swimming can improve neuropathic pain (NPP) through alterations of cells that constitute the spinal dorsal horn,brainstem and injured peripheral nerve, but the exact mechanisms under lying exercise–induced hypoalgesia (EIH) are not fully understood. Since effects of physical exercise are influ enced by many factors including intensity, duration, frequency and style (forced exercise vs voluntary exercise) of exercise, the most suitable condition of exercise to produce EIH have not yet been determined in detail. The purpose of this review article is to compare the effects of forced treadmill running (FTR) and voluntary wheel running (VWR) in producing EIH in order to propose optimum exercise conditions to induce EIH. In addition, we described several potential mechanisms under lying EIH. In the case of FTR, we have demonstrated that exercise conditions composed of 1) acclimation to FTR prior to surgery, 2) initiation of FTR at an early stage after surgery and 3) enforcement of FTR for 60 min ⁄day, 5 days ⁄ week at low– or intermediate–exercise intensity are most effective in producing EIH. We further demonstrated that VWR can not only sufficiently produce EIH, but also improve pain behaviors more efficiently than FTR does. Our study suggested that initiation of VWR without delay after surgery may be an important factor to develop EIH. On the other hand, despite growing evidence showing the importance of γ–aminobutyric acid (GABA) and glutamic acid decarboxylase (GAD) 65 and 67 in the regula tion of NPP, the relevance of both factors to EIH is totally unknown. Immunofluorescence analysis showed that VWR significantly prevents sciatic nerve injury–induced reductions in GAD65 production in the superficial dorsal horn, and suggested that maintained GAD65 production may consequently contribute to the retention of GABA in interneurons and neuropils of the dorsal horn. Based on these findings, we propose that EIH is achieved, at least in part, by maintaining GABAergic inhibition in the spinal dorsal horn, and that VWR may be a potentially most suitable exercise style for producing EIH.

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   Objective. To analyze the intramyocellular lipids (IMCL) and extramyo -cellular lipids (EMCL) in the multifidus muscle (Mm) using magnetic resonance spectroscopy (MRS) with chronic low back pain (LBP) patients and to identify possible correlation with LBP, obesity and these metabolism.
   Materials and Methods. This prospective study had institutional review board approval, and written informed consent was obtained from all study participants. Forty patients (24 women, 16 men; mean age, 64.7 years ± 12.7; age range, 22–85 years) with LBP duration of ≥ 3 months, who underwent MRS to quantify IMCL and EMCL of right Mm in a volume interest at the intervertebral level of L4 through L5. We analyzed body mass index (BMI) as an indicator of obesity, and visual analogue score (VAS) as LBP intensity. The associations were analyzed using Spearman's correlation coefficient.
   Results. The BMI showed correlation with EMCL (r=0.436, p<0.01), but no correlation with IMCL. The VAS showed correlation with IMCL (r= 0.657, p<0.01) but no correlation with EMCL.
   Conclusion. The present study showed a relationship between IMCL in the Mm and chronic LBP. The analysis of Mm with MRS is expected to become an effective objective indicator of chronic LBP.

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