In a previous study, the authors have suggested that there is a central mechanism in pain modulation of TENS, and interferential current therapy(ICT) by using the tail-flick reflex and measuring the cerebrospinal fluid beta-endorphin of the rat. To confirm this central opiate-mediated pain modulation, we examined the reversal of a delayed tail-flick reflex latency and the cerebrospinal fluid beta-endorphin level by the naloxone administration. We measured the latencies of fictive tail-flick reflex before, immediately after TENS, ICT, and 15 minutes after naloxone administration. Cerebrospinal fluid beta-endorphin was also measured quantitatively by radioimmunoassay after TENS, ICT and naloxone administration. The results revealed that in the group with TENS application, the latency of tail flick reflex after naloxone administration(31.54+/-5.08) was reversed to the level before the TENS application(34.76+/-6.09 msec) compared to the level after the TENS application(were 42.28+/-10.14 msec). With ICT application, the latency of tail flick reflex after naloxone administration(32.46+/-5.52msec) was also reversed to the level before the ICT (33.39+/-4.72 msec) application compared to the level immediately after the ICT application(46.87+/-10.14 msec). The beta-endorphin levels in cerebrospinal fluid were significantly decreased in the groups of naloxone administration, both with the TENS(14.86+/-3.92 pmol/l) and the ICT applications(18.04+/-3.93 pmol/l) compared to the control group(52.05+/-14.12 pmol/l). We confirmed that the central pain modulation mechanism of TENS and ICT was through the reversal of delayed tail-flick reflex latency and elevated CSF beta-endorphin level after naloxone administration
Animals ; beta-Endorphin* ; Cerebrospinal Fluid ; Naloxone* ; Radioimmunoassay ; Rats* ; Reflex* ; Transcutaneous Electric Nerve Stimulation*

As use of the visual display terminal (VDT) is becoming more generalized as a result of office automation, the so-called 'VDT syndrome' which is often observed with the workers using VDT has emerged as a serious occupational health problem. However, few comparative study with control group using not only subjective symptom but also physical examination hag been conducted. We have conducted a study comparing prevalence rates of musculoskeletal disorder between 113 VDT operators of a telecommunication company and the control groups of housewives and office ladies through a review of subjective symptoms as well as physical examination by physiatrist to understand the magnitude of problem and relative risk of VDT worker. The symptom rates of upper extremity disability in VDT operators were higher than those of controls especially in neck and shoulder area. Fifty-four(47.8%) of 113 VDT operators met our case definition of upper extremity disorder by subjective symptom and physical examination. Myofascial pain syndrome of neck and shoulder muscles were the most common(46.9%). The odd ratio of using VDT operation for developing myofascial pain syndrome in the neck or shoulder area were 2.52(compared to controls of office ladies) and 2.64 (compared to controls of housewives). Other anatomical lesion such as elbow, hand and wrist shows slight higher prevalence rates of musculoskeletal disorder than control groups but not statistically significant.
Elbow ; Hand ; Muscles ; Myofascial Pain Syndromes ; Neck ; Occupational Health ; Office Automation ; Physical Examination ; Prevalence ; Shoulder ; Telecommunications ; Upper Extremity ; Wrist