Spatial learning and memory deficits induced by exposure to iron-56-particle radiation

It has previously been shown that exposing rats to particles of high energy and charge (HZE) disrupts the functioning of the dopaminergic system and b ehaviors mediated by this system, such as motor performance and an amphetam ine-induced conditioned taste aversion; these adverse behavioral and neuron al effects are similar to those seen in aged animals. Because cognition dec lines with age, spatial learning and memory were assessed in the Morris wat er maze 1 month after whole-body irradiation with 1.5 Gy of 1 GeV/nucleon h igh-energy Fe-56 particles, to test the cognitive behavioral consequences o f radiation exposure. Irradiated rats demonstrated cognitive impairment com pared to the control group as seen in their increased latencies to find the hidden platform, particularly on the reversal day when the platform was mo ved to the opposite quadrant. Also, the irradiated group used nonspatial st rategies during the probe trials (swim with no platform), i.e. less time sp ent in the platform quadrant, fewer crossings of and less time spent in the previous platform location, and longer latencies to the previous platform location. These findings are similar to those seen in aged rats, suggesting that an increased release of reactive oxygen species may be responsible fo r the induction of radiation- and age-related cognitive deficits. If these decrements in behavior also occur in humans, they may impair the ability of astronauts to perform critical tasks during long-term space travel beyond the magnetosphere. (C) 2000 by Radiation Research Society.