title: Enhanced cued fear memory following post-training whole body irradiation of 3-month-old mice.
abstract: Typically, in studies designed to assess effects of irradiation on cognitive performance the animals are trained and tested for cognitive function following irradiation. Little is known about post-training effects of irradiation on cognitive performance. In the current study, 3-month-old male mice were irradiated with X-rays 24h following training in a fear conditioning paradigm and cognitively tested starting two weeks later. Average motion during the extinction trials, measures of anxiety in the elevated zero maze, and body weight changes over the course of the study were assessed as well. Exposure to whole body irradiation 24h following training in a fear conditioning resulted in greater freezing levels 2 weeks after training. In addition, motion during both contextual and cued extinction trials was lower in irradiated than sham-irradiated mice. In mice trained for cued fear conditioning, activity levels in the elevated zero maze 12days after sham-irradiation or irradiation were also lower in irradiated than sham-irradiated mice. Finally, the trajectory of body weight changes was affected by irradiation, with lower body weights in irradiated than sham-irradiated mice, with the most profound effect 7days after training. These effects were associated with reduced c-Myc protein levels in the amygdala of the irradiated mice. These data indicate that whole body X ray irradiation of mice at 3 months of age causes persistent alterations in the fear response and activity levels in a novel environment, while the effects on body weight seem more transient.
authors.affiliation: Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Reid H J
authors.initials: RH
authors.lastname: Olsen
authors.affiliation: Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Sydney J
authors.initials: SJ
authors.lastname: Weber
authors.affiliation: Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Tunde
authors.initials: T
authors.lastname: Akinyeke
authors.affiliation: Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA; Departments of Neurology and Radiation Medicine, Division of Neuroscience, ONPRC, Oregon Health & Science University, Portland, OR 97239, USA. Electronic address: raberj@ohsu.edu.
authors.forename: Jacob
authors.initials: J
authors.lastname: Raber
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000528:radiation effects; D001921:Brain / Q000528:radiation effects; D003213:Conditioning, Psychological / Q000528:radiation effects*; D003463:Cues; D004597:Electroshock / Q000009:adverse effects; D005239:Fear / Q000528:radiation effects*; D046352:Freezing Reaction, Cataleptic / Q000528:radiation effects; D008297:Male; D018782:Maze Learning / Q000528:radiation effects; D008568:Memory / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000528:radiation effects; D014916:Whole-Body Irradiation
keywords: Body weight; Cued fear; Irradiation; Post-training; Zero maze