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Neuroscience. 2001;103(4):1043-50.

Fragile X mice develop sensory hyperreactivity to auditory stimuli.

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1
Department of Pharmacology, Weill Medical College of Cornell University, 1300 York Avenue, LC 522, New York, NY 10021, USA.

Abstract

Fragile X syndrome is the most prevalent cause of mental retardation. It is usually caused by the transcriptional inactivation of the FMR-1 gene. Although the cognitive defect is the most recognized symptom of fragile X syndrome, patients also show behavioral problems such as hyperarousal, hyperactivity, autism, aggression, anxiety and increased sensitivity to sensory stimuli. Here we investigated whether fragile X mice (fmr-1 gene knockout mice) exhibit abnormal sensitivity to sensory stimuli. First, hyperreactivity of fragile X mice to auditory stimulus was indicated in the prepulse inhibition paradigm. A moderately intense prepulse tone, that suppresses startle response to a strong auditory stimulus, elicited a significantly stronger effect in fragile X than in control mice. Second, sensory hyperreactivity of fragile X mice was demonstrated by a high seizure susceptibility to auditory stimulation. Selective induction of c-Fos, an early-immediate gene product, indicated that seizures involve auditory brainstem and thalamic nuclei. Audiogenic seizures were not due to a general increase in brain excitability because three different chemical convulsants (kainic acid, bicuculline and pentylenetetrazole) elicited similar effects in fragile X and wild-type mice. These data are consistent with the increased responsiveness of fragile X patients to auditory stimuli. The auditory hypersensitivity suggests an abnormal processing in the auditory system of fragile X mice, which could provide a useful model to study the molecular and cellular changes underlying fragile X syndrome.

PMID:
11301211
[Indexed for MEDLINE]
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