Radiation-induced cognitive dysfunction in 4-month old male wistar rat

Behavioral dysfunction of memory process arising 4 months after whole brain irradiation (30 Gy/10 fractions/12 days) has been demonstrated in 16-27 month old rats, as compared with non irradiated rats. This study was therefore aimed at delivering the same irradiation in young rats and comparing results with those previously obtained in old rats. Thirty-three 4-month old rats were included into the study. Eighteen received whole brain irradiation (30 Gy/10 fractions/12 days), and 18 were given sham irradiation. Sequential behavior studies were done before irradiation and during the 7 months following irradiation. Significant decrease in memory function was observed in irradiated rats 1 month (p<0.001), 3 months (p<0.013), and 6 months (p=0.007) post-irradiation. This was accompanied by learning deficit 1 month (p=0.01), 4.5 months (p=0.003), and 7 months (p=0.009) post-irradiation. Response to radiation therapy observed in young rats differed from that observed in old rats. Young rats showed earlier decrease in memory function than old rats, but this deficit also arose earlier in young rats than in old rats. In two cases this deficit was permanent. (authors)