| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
It is abundantly clear that there are major differences between acute and chronic Pain. However, many animal studies for pain and nociception employ short- lasting noxious stimuli which may have limited relevance to prolonged or chronic pain states.
In this study, we provide a new rat tonic pain model developed in our laboratory, which is characterized by recording rat's hind paw flexion responses with the passage of time after dilute formalin injection. The response burst,15 responses and more per minute, were constantly induced for at least 45 minutes, i.e., from 25 to 70 minutes after formalin injection, and were considered to be due to tonic nociception of the animal because of their high sensitivity to morphine.
A few animals were showed poor responses (5 responses and less per minute) consistently. The inhibition of formalin induced flexion responses observed in these animals were estimated to be mediated by endogenous opioid systems, for those inhibitions were antagonized by naloxion, opioids antagonist.
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