THE EFFECT OF SYMPATHOMIMETIC AMINES ON RADIATION-INDUCED TOLERANCE TO PENTOBARBITAL IN THE RAT
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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Male Sprague-Dawley rats were given 250-, 500-, or 1000-rad midline tissue doses of 300 kVp x rays. Twenty-four hours postirradiation the acute toxicity of sodium pentobarbital was determined in these animals. Rats receiving 500 and 1000 rads demonstrated an increased tolerance to sodium pentobarbital, but no change in toxicity was observed in animals given 250 rads. This radiation-induced increase in pentobarbital tolerance was similar in degree to that observed in unirradiated rats treated with amphetamine, a known barbiturate antagonist. However, when rats received amphetamine as well as 1000 rads of x rays no increased tolerance to sodium pentobarbital was observed. Four days of reserpine treatment prior to irradiation also abolished the radiation- induced increase in sodium pentobarbital tolerance. These results suggest that increased central norepinephrine levels are responsible for the radiation- induced increase in tolerance to pentobarbital.