The Interactive Effects of Morphine and Ionizing Radiation on the Latency of Tail-Withdrawal from Warm Water in the Rat,
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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The analgesic effect of morphine was enhanced in rats exposed to ionizing radiation 250-5000 in a dose-dependent manner. This was indicated by an increase in the latency of tail-withdrawal from warm water, compared with animals receiving morphine alone. Radiation alone had no effect on latencies or on gross behavior. The enhancing effect of radiation was strongest at 24 hours after irradiation and was partially reversible with naloxone, an opiate antagonist, at a dose of 2 mgkg, i.m. No changes in survival time after irradiation were noted between animals receiving morphine and those receiving saline injections. The results of this study suggest that the effect of narcotic analgesics to relieve pain in casualties on a nuclear battlefield may be enhanced depending on the postirradiation interval.