The Korean Journal of Physiology
- Volume 23 Issue 1
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- Pages.139-149
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- 1989
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- 0300-4015(pISSN)
Electrophysiologic Mechanism of Tail Flick Reflex in Rats
흰쥐 Tail Flick Reflex의 신경생리학적 기전
- Seoh, Sang-Ah (Department of Physiology, College of Medicine, Kyungsang National University) ;
- Kim, Jun (Department of Physiology, College of Medicine, Seoul National University)
- Published : 1989.06.30
Abstract
Although tail flick reflex (TFR) in rats has been used as a classic model of the nociceptive test to evaluate the action of analgesics, there have been few studies on the origin of the latent period of TFR. Present study was performed to elucidate the mechanism of increase in latency of TFR by morphine in anesthetized rats. Tail skin and dorsolateral tail nerve were stimulated electrically and EMG activities were recorded from abductor caudae dorsalis muscle participating in tail flick reflex. In the case of noxious radiant heat stimulation to tail, the tail flick tension was recorded before and after administration of morphine. Then changes in latency and conduction velocity of peripheral nerve were evaluated. The results obtained were as follows: 1) The latencies of TFR evoked by the electrical stimulation of tail skin and dorsolateral tail nerve were all within 40 ms and were elongated by several milliseconds from control after the administration of morphine. Peripheral conduction velocities of tail flick afferent nerve were within the range of 10-25 m/s. 2) The conduction velocity of peripheral nerve was significantly reduced after morphine administration, therefore the afferent time (utilization time+conduction time to spinal cord) was significantly increased. But the time for central delay and efferent time was not affected by morphine. 3) The conduction velocity under room temperature