Dose-Rate Effects of Co60Irradiation on Performance and Physiology in Monkeys.

摘要

One thousand rad Co60 was administered to 12 monkeys at 75 rad/min and to 8 monkeys at 50 rad/min while they performed a delayed match-to-sample, shock avoidance task. Only four at 75 rad/min and two at 50 rad/min showed early performance decrement and/or early transient incapacitation (PD-ETI), in contrast to 13 of 16 previously studied monkeys who showed PD-ETI with an average dose rate of 180 rad/min. A dose-rate effect was concluded. When these three groups were compared with an untrained group exposed to a 4000-rad gamma-neutron pulse, all showed similar degrees of hypotension postirradiation. But the onset of hypotension was delayed and its rate of fall prolonged as dose rate decreased. Tentative interpretation was that radiation thresholds for the induction of PD-ETI exist for cumulative dose (> or = 300 rad, midbody) and dose rate (> or = 30 rad/min).