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.