POSTER PRESENTATION ABSTRACTS
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Salons 10-12.
THURSDAY, 5:30-6:15 PM
Whittaker P.
Laser acupuncture exerts an opioid-mediated analgesic
effect.
University of Massachusetts Medical School Peter.whittaker@umassmed.edu
PURPOSE: Needle acupuncture, in addition to
electro- and laser acupuncture, has been used clinically to relieve
pain. Although human pain quantification is difficult and often subjective,
in rodent models the tail-flick test provides a well-established and
objective analgesia assessment. This test measures the time taken before
a rat withdraws its tail from a heat source. Needle and electro-acupuncture
at points Spleen-6 (at the tibia's posterior margin) and Stomach-36
(just below the knee, lateral to the tibia) have been found to increase
tail-flick time in rats. We aimed to determine if laser acupuncture
had a similar effect.
METHODS: Female Sprague-Dawley rats were habituated
to handling before the study. We treated the two acupuncture points
and a sham, non-acupuncture point on the tail (dorsal surface, 1 cm
from the base) for 2 minutes (690 nm, 130 mW). The baseline tail-flick
time was measured first; 5 measurements 2 minutes apart were averaged.
Two hours later, laser acupuncture was performed and tail-flick time
remeasured 10 minutes after treatment. The next day, an intraperitoneal
injection of the non-specific opioid-blocker naloxone was given (20
mg/kg). One hour later, laser acupuncture was performed and tail-flick
time measured.
RESULTS: All groups had a baseline tail-flick
time of ~ 3s. This time was not increased after direct tail irradiation
(3.5 ± 0.1 vs baseline 3.3 ± 0.1s; P = NS). In contrast, irradiation
of Spleen-6 increased tail-flick time (3.9 ± 0.1 vs baseline 3.2 ± 0.1s;
P<0.05). This increase was significantly attenuated by naloxone (3.4
± 0.1s; P=NS vs baseline). Similarly, tail-flick time increased after
Stomach-36 irradiation and was again blocked by naloxone.
CONCLUSION: Laser acupuncture exerts an analgesic
effect via an opioid-mediated mechanism.
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