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KMID : 0382619960160020259
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Hanyang Journal of Medicine
1996 Volume.16 No. 2 p.259 ~ p.272
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Effect of T-irradiation on the opioid-induced analgesia
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Abstract
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Although radiotherapy has been used for the relief of pain almost for a century, there remain much to be explained about its exact mechanisms and values in controlling cancer pain. In contrast to analgesic effect, ionizing radiation is also known to alter the acute antinociceptive effect of morphine.
To study effect of γ-irradiation on the antinociceptive action of opioid, tail-flick latency was measured in the Sprague-Dawley rat exposed to γ-irradiation (5Gy and 20Gy) after intraperitoneal administration of fentanyl (100㎍/㎏). Also studied was effect of γ-irradiation on the fentanyl-induced changes in the responses of WDR cells to electrical or thermal Stimulations in cats. The results of the present study are summarized as follows:
1. γ-irradiation did not affect nociceptive reflex in tail-flick test in the rat.
2. Analgesic effect of fentanyl was markedly suppressed in rats whose head or whole body had been exposed to γ-irradiation. However the suppressed fentanyl effect was restored to normal level in 7 days after exposure of rats to γ-irradiation.
3. The A-fiber responses of WDR cells were not altered by intravenous(20㎍/㎏) or spinal (150㎍%) application of fentanyl both in the irradiated and non-irradiated cats.
4. The C-fiber responses of WDR cells were strongly suppressed by intravenously administered or spinally applied fentanyl. This fentanyl-induced depression in the WDR cell responses was significantly alleviated by γ-irradiation only when fentanyl were administered intravenously.
5. The responses of WDR cells to thermal stimulation (44℃ & 48℃) were markedly suppressed by fentanyl. In contrast of C-fiber responses, thermal responses of WDR cells were more prominently suppressed when fentanyl was applied directly on spinal cord. The fentanyl-induced (iv & spinal application) depression in the thermal responses of WDR cells was significantly alleviated by γ-irradiation.
These results suggest that γ-irradiation alleviates analgesic effect of opioid and that selection and dosage of the analgesics are important in the pain control of the cancer patients.
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