Total body 4.5 Gy gamma irradiation-induced early delayed learning and memory dysfunction in the rat

In an attempt to determine the consequences of total body radiation damage on learning and memory in the rat, twenty-eight male Wistar rats aged 4 mon ths received 4.5 Gy total body gamma -irradiation (TBI) while 28 rats recei ved sham irradiation. Sequential behavioral studies of negative reinforceme nt including a/ one- and b/ two-way avoidance tasks were undertaken, a/ One -way avoidance test: this test was performed before and after TBI. Prior to irradiation both groups were similar. At 20 days (D) and at 3 months post- TBI, irradiated rats had a significantly lower percentage of avoidance than controls but no statistical difference was found at 5 months post-TBI. b/ Two-way avoidance test: this test was performed only after TBI. At days 21, 22, 23, 24, (learning) and at 3 or 6 months (recalls) post-TBI the mean pe rcentage of avoidance was significantly lower in irradiated than in control rats. This study demonstrates that total-body exposure to 4.5 Gy gamma -ir radiation induces behavioral dysfunction affecting learning and transitoril y memory. These results suggest that a relatively low; dose of total body i rradiation can induce neurological complications. which persist 4-6 months later.