RESUMO
[Objective] To confirm the validity of chronic pain model due to a soft tissue lesion, we examined and compared pain behaviors occurring at the site of the lesion and a remote area.<BR>[Methods] To produce muscle lesion in rats, lipopolysaccharide (LPS, 2 μg/kg, 100 μl) and 6% hypertonic saline (HS, 100 μl, five consecutive injections at 90-minite intervals) were injected into the unilateral gastrocnemius muscle at 24-hour intervals. Then, measurements for the muscle pain threshold and mechanical hypersensitivity of the hind paw were performed bilaterally. <BR>[Results] A combined treatment with LPS and HS to the unilateral muscle developed long-persisting pain behaviors in the hind paws bilaterally, lasting more than 10 weeks. On the other hand, pain behavior at the injected site disappeared within 1 week after treatment.<BR>[Conclusion] The pain behavior occurring beyond the site of the lesion persists even after the disappearance of pain in the muscle, showing a similar pattern in the development of chronic pain seen in humans.
RESUMO
Peripheral mechanisms that induce analgesic effects in manual acupuncture were studied in urethane-anesthetized rats. Unitary extracellular recordings were made from spinal wide dynamic range (WDR) neurons and repetitive electrical stimuli were delivered to the excitatory receptive fields to determine a noxious index. First, the analgesic effects of manual acupuncture and a noxious pinch to the skin (Diffuse Noxious Inhibitory Controls: DNIC) were compared. Second, manual acupuncture was applied to different structures at the acupuncture point, such as the skin, skin plus muscle, and muscle. In a third experiment, the analgesic effects of intramuscular injection of 4.5% NaCl and manual acupuncuture were compared. Manual acupuncture and a noxious pinch exhibited a very similar time course and magnitude of inhibitory effects on C-evoked discharges. As for differential stimulation of the acupuncture point, application of the needle to the skin only was less effective than to the skin plus muscle or the muscle only. Both intramuscular injection of 4.5% NaCl and manual acupuncture reduced C-evoked discharges while injection of isotonic saline produced almost no inhibitory effects. These data suggest that application of manual acupuncture might arouse noxious sensations that result in activating pain inhibitory processes. Moreover, it is thought that excitation of polymodal receptors in the muscle is a critical factor in inducing analgesic effects in manual acupuncture.
RESUMO
Manual acupuncture to ST 36 Zusanli induces both long-lasting and short-term inhibitory effects on C-evoked discharges of wide dynamic range (WDR) neurons in the lumbar cord. The possible involvement of the central nervous system in producing these two types of inhibitions was investigated in urethane-anesthetized rats. In one expriment, the existence of a descending pain inhibitory system was studied using spinal conduction blocks at the cervical level. In a separate experiment, naloxone was administered systemically to investigate the participation of endogenous opioids.<br>Long-lasting inhibition was found to be due to a descending pain inhibitory system from the upper central nervous system together with the involvement of an opioidergic link. On the other hand, short-term inhibition was attributed to a propriospinal pain inhibitory system and endogenous opioids were not implicated.
RESUMO
In 1987, Yamamoto developed Initial Skin Temperature Controlled Repeated Thermal Stimulation System (STRTS), consisting of microcomputer PC-9801 (NEC Co.) and the pain meter NYT-55 (KUDO ELECTRIC Co.) which was modified type of Hardy's algometer. We used STRTS to establish more simple and accurate evaluation of the effects of electroacupuncture (EA).<br>Five female volunteer subjects with mean age of 21.8 were involved in this measurement. Radiant heat stimuli of 200mcal/sec/cm<sup>2</sup> were repeatedly delivered to six different skin areas on the left body surface where blackened sticky tape were applied. Stainless acupuncture needles were inserted into LI4 Hegu _??__??_ until subjects felt a typical sensation called De Qi. Both Hegu were stimulated electrically with 4 and 10Hz for 30 minutes. We measured pain threshold repeatedly before and after an EA with the passage of time.<br>EA generally raised pain threshold of measuring points, especially the neck and forehead. In some cases, however, pain thresholds of several points were reduced by EA. These results suggested that effects of EA varied with the subjects. As for frequency of EA, 4Hz was much effective than that of 10Hz.