title: Mouse model of fragile X syndrome: behavioral and hormonal response to stressors.
abstract: Fragile X syndrome, a form of mental retardation caused by inadequate levels of fragile X mental retardation protein (FMRP), is characterized by extreme sensitivity to sensory stimuli and increased behavioral and hormonal reactivity to stressors. Fmr1 knockout mice lack FMRP and exhibit abnormal responses to auditory stimuli. This study sought to determine whether Fmr1 knockout mice on an F1 hybrid background are normal in their response to footshock. Knockout mice were also examined for signs of hyperexcitation across an extended trial range, and serum corticosterone levels were evaluated in response to various stressors. The ability to acquire conditioned taste aversion was also assessed. Knockout mice exhibited no impairment in associative aversive learning or memory, since they successfully expressed conditioned taste aversion. Footshock-sensitivity, freezing behavior, and corticosterone response to various stressors did not differ between knockout and wild-type mice. However, knockout mice exhibited significantly increased responses during the extended test. The knockout mice's increased responsiveness to footshock in the extended test may be an indication of increased vulnerability to stress or enhanced emotional reactivity.
authors.affiliation: Department of Pediatrics, University of Colorado Denver Medical School, Aurora, CO 80045, USA.
authors.forename: Darci M
authors.initials: DM
authors.lastname: Nielsen
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Evans
authors.forename: William J
authors.initials: WJ
authors.lastname: Derber
authors.forename: Kenzie A
authors.initials: KA
authors.lastname: Johnston
authors.forename: Mark L
authors.initials: ML
authors.lastname: Laudenslager
authors.forename: Linda S
authors.initials: LS
authors.lastname: Crnic
authors.forename: Kenneth N
authors.initials: KN
authors.lastname: Maclean
mesh_terms: D000818:Animals; D001245:Association Learning / Q000502:physiology; D001362:Avoidance Learning / Q000502:physiology; D003213:Conditioning, Psychological / Q000502:physiology; D003345:Corticosterone / Q000097:blood; D004195:Disease Models, Animal; D004597:Electroshock; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics; D005600:Fragile X Syndrome / Q000503:physiopathology* / Q000523:psychology*; D046352:Freezing Reaction, Cataleptic; D008297:Male; D008568:Memory / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000503:physiopathology*; D013550:Swimming; D013649:Taste
chemical_list: D003345:Corticosterone; D051860:Fragile X Messenger Ribonucleoprotein 1; C497684:Fmr1 protein, mouse