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Title: Effects of head-only or whole-body exposure to very low doses of 4HE (1000 MeV/n) particles

Author
item RABIN, BERNARD - University Of Maryland
item POULOSE, SHIBU - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item Miller, Marshall
item BIELINSKI, DONNA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item Kelly, Megan
item CARRIHILL-KNOLL, KIRSTY - University Of Maryland
item PATEL, RISHIT - University Of Maryland
item HAWKINS, ELIZABETH - University Of Maryland
item HENG, RANDY - University Of Maryland
item Shukitt-Hale, Barbara

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/5/2016
Publication Date: 1/23/2017
Citation: Rabin, B.M., Poulose, S., Miller, M.G., Bielinski, D.F., Kelly, M.E., Carrihill-Knoll, K.L., Patel, R., Hawkins, E., Heng, R., Shukitt Hale, B. 2017. Effects of head-only or whole-body exposure to very low doses of 4HE (1000 MeV/n) particles. [Abstract]. NASA Human Research Program Investigators' Workshop, Program #17271.

Interpretive Summary:

Technical Abstract: INTRODUCTION On exploratory class missions, astronauts will be exposed to a range of heavy particles which vary in linear energy transfer (LET). Previous research has shown a direct relationship between particle LET and cognitive performance such that, as particle LET decreases the dose needed to affect cognitive performance also decreases. Because a significant portion of the total dose experienced by astronauts may be expected to come from exposure to low LET 4He particles, it would be important to establish the threshold dose of 4He particles that can produce changes in cognitive performance. METHODS Sprague-Dawley rats weighing between 200-225 g were given either head-only or whole-body exposures to 4He particles (1000 MeV/n) at doses ranging from 0.01 to 0.5 cGy. Following exposure, the brains were removed from a subset of the rats (n = 5/dose) for analysis of oxidative stress by measuring NADPH oxidase (NOX2) expression. Measurements were also made of phosphorylated-cyclic AMP (cAMP)-responsive element-binding protein (CREB) and nuclear factor E2-related factor 2 (Nrf2). The remaining rats (n = 10/dose) were shipped to UMBC for behavioral testing. Behavioral tests included: elevated plus maze (baseline anxiety); novel object and novel spatial recognition (learning and memory); and operant responding on an ascending fixed-ratio schedule (motivation to work for reward and responsiveness to environmental contingencies). RESULTS The results indicated that changes in behavioral endpoints could be observed following exposures to 4He particles at doses as low as 0.01 to 0.025 cGy. Differences in neurochemical endpoints were observed following exposure to doses as low as 0.05 cGy (the lowest dose tested). There were no significant differences between head-only and whole-body exposures on behavioral performance. Preliminary analyses of the neurochemical data suggest that whole body exposures may not have been as effective in producing changes in neuronal functioning as were head-only exposures. DISCUSSION Because 4He particles will constitute a significant fraction of the radiation dose to which astronauts will be exposed, the present results, therefore, suggest the possibility that astronauts on exploratory class missions may be at a greater risk for HZE-induced cognitive deficits than anticipated.