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The purposes of this study were 1 ) to examine the effect of high intensity , low frequency transcutaneous electrical nerve stimulation at auricular acupuncture points on experimental pain threshold measured at the wrist and 2 ) to determine the changes in effect over time .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
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