Interaction between age and exposure to 56Fe particles on behavior and neurochemistry

Authors: CAREY, AMANDA - NORTHEASTERN UNIVERSITY; Shukitt-Hale, Barbara; RABIN, BERNARD - UMBC; Joseph, James

Submitted to: Advances in Space Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2006
Publication Date: 3/15/2007
Citation: Carey, A.N., Shukitt Hale, B., Rabin, B.M., Joseph, J.A. 2007. Interaction between age and exposure to 56Fe particles on behavior and neurochemistry. Advances in Space Research. 39:987-993.

Interpretive Summary: Previous research has shown that exposure to radiation particles, which will be encountered on long-term space missions, can adversely affect the ability of rats to perform in a variety of behavioral tasks. This outcome has implications for an astronaut's ability to successfully complete mission requirements. It has also been found that irradiation can lead to increases in oxidative stress, which can have a variety of negative effects in the body, similar to that seen in the aging brain. Given that astronauts are often middle-aged or older, it is important to determine if their age puts them at higher risk for the potentially hazardous effects of exposure to high-energy radiation particles. Therefore, we exposed young and old rats to different doses of iron irradiation and evaluated their performance in a spatial learning and memory task, in addition to examining levels of a brain chemical. Results indicated that exposure to iron particles can produce alterations in memory behavior and brain cell signaling and that these alterations may be more apparent in older animals, a finding which suggests that the aging brain may be more susceptible to the deleterious effects of irradiation on performance. Therefore, age may be a factor for consideration in planning long-term missions into space.

Technical Abstract: Previous research has shown that exposure to HZE particles, which will be encountered on long-term space missions, can adversely affect the ability of rats to perform a variety of behavioral tasks. This outcome has implications for an astronaut's ability to successfully complete requirements associated with these missions. It has also been found that irradiation can lead to increases in oxidative stress, similar to that seen in the aging brain. Given that astronauts are often middle-aged or older it is important to determine if their age puts them at higher risk for the potentially hazardous effects of exposure to HZE particles. Therefore, we exposed young (7 mos) and old (16 mos) male Fischer 344 rats to either 1 or 2Gy of 1 GeV/n 56Fe particle irradiation at a nominal dose rate of 1.0-1.5Gy/min at the National Space Radiation Laboratory at Brookhaven National Laboratory. Control rats were not exposed to the beam. Rats were then tested in the Morris water maze, a spatial learning and memory task, for four consecutive days (6 trials/day) 6-7 weeks after irradiation when they were approximately 9 and 18 months of age. Muscarinic enhancement of DA release from superfused striatal slices, an indicator of receptor sensitivity and striatal function and integrity, was conducted 4 weeks following behavioral testing, when rats were approximately 10 and 19 months of age. Results indicated that exposure to 56Fe particles can produce alterations in behavior and neuronal signaling and that these alterations may be more apparent in older organisms, a finding which suggests that the aging brain may be more susceptible to the deleterious effects of irradiation on performance. Therefore, age may be a factor for consideration in planning long-term missions into space.