Effects of Proton Radiation and Pomegranates on Hippocampus and Behavior

Exposure to ionizing radiation may have deleterious effects on physical and mental health, with an increased risk of proton radiation for astronauts traveling outside Earth's atmosphere into lower earth orbit. In animal models, radiation has been shown to suppress neurogenesis in the subgranular zone of the hippocampus, a key area for learning and memory. Furthermore, some evidence suggests that compounds found in fruits and vegetables (e.g. polyphenols) may offer some protection against the cellular effects of radiation. Few studies have looked at the effects of proton radiation on the central nervous system, even though proton radiation is the most prevalent ionizing radiation in space. This study determined whether a polyphenol-rich diet could offer enough protection from the effects of radiation to maintain complex cognitive and fine motor skills such as those required by astronauts. Ninety-six C57BL/6 mice (48 receiving pomegranate juice and 48 receiving sugar water control in their drinking bottles) underwent a battery of behavioral tests to assess baseline cognitive and motor functions and were then either irradiated with proton radiation (2 Gy at 150 MeV/n at 1-2 Gy/min) or sham irradiated. 2 Gy is the approximate dose of radiation to which an astronaut on a long-term mission to Mars may be exposed. Post-radiation behaviors were assessed 1-2 days after irradiation and again two months later to determine radiation-related behavioral changes. Radiation affected depression- and avoidance behaviors. Pomegranate juice was found to be protective against radiation-induced depression, but had gender-specific affects for avoidance behavior. In addition, pomegranate juice seemed to have a greater effect on males than females, inducing behavior similar to that of females in tests of motor coordination and activity levels. Furthermore, the birth of new glial cells and neurons in the hippocampus was quantified using immunohistochemistry for BrdU+/DCX+ cells. Radiation suppressed cell proliferation (BrdU+) and neurogenesis in the dentate gyrus (BrdU+/DCX+) of the hippocampus. Pomegranate juice increased neurogenesis (DCX+) in the hippocampus of non-irradiated mice. These data highlight the importance of understanding the complex gender-specific interactions between diet, behavior, and neuropathology, and suggest that pomegranate juice may protect against some radiation-induced deficits.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Psychology

Year

2013

Author dc:creator

• Dulcich, Melissa S.

Contributors dc:contributor

• Hartman, Richard E.
• Haerich, Paul
• Pop, Viorela
• Vermeersch, David

• Experimental Analysis of Behavior
• Ionizing radiation - toxicology; Radiation effects; Antioxidants;
• Proton radiation
• Pomegranates
• Hippocampus
• Behavior
• Ionizing radiation
• Antioxidants
• Neurogenesis
• Central nervous system
• Polyphenols
• Radiation-induced depression

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/119

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-1118