Impaired inhibitory control of cortical synchronization in fragile X syndrome

J Neurophysiol. 2011 Nov;106(5):2264-72. doi: 10.1152/jn.00421.2011. Epub 2011 Jul 27.


Fragile X syndrome (FXS) is a neurodevelopmental disorder characterized by severe cognitive impairments, sensory hypersensitivity, and comorbidities with autism and epilepsy. Fmr1 knockout (KO) mouse models of FXS exhibit alterations in excitatory and inhibitory neurotransmission, but it is largely unknown how aberrant function of specific neuronal subtypes contributes to these deficits. In this study we show specific inhibitory circuit dysfunction in layer II/III of somatosensory cortex of Fmr1 KO mice. We demonstrate reduced activation of somatostatin-expressing low-threshold-spiking (LTS) interneurons in response to the group I metabotropic glutamate receptor (mGluR) agonist 3,5-dihydroxyphenylglycine (DHPG) in Fmr1 KO mice, resulting in impaired synaptic inhibition. Paired recordings from pyramidal neurons revealed reductions in synchronized synaptic inhibition and coordinated spike synchrony in response to DHPG, indicating a weakened LTS interneuron network in Fmr1 KO mice. Together, these findings reveal a functional defect in a single subtype of cortical interneuron in Fmr1 KO mice. This defect is linked to altered activity of the cortical network in line with the FXS phenotype.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Cortical Synchronization / physiology*
  • Fragile X Mental Retardation Protein / genetics*
  • Fragile X Syndrome / genetics
  • Fragile X Syndrome / physiopathology*
  • Interneurons / physiology
  • Male
  • Methoxyhydroxyphenylglycol / analogs & derivatives
  • Methoxyhydroxyphenylglycol / pharmacology
  • Mice
  • Mice, Inbred Strains
  • Mice, Knockout
  • Neural Inhibition / physiology*
  • Organ Culture Techniques
  • Phenotype
  • Pyramidal Cells / physiology
  • Receptors, Metabotropic Glutamate / agonists
  • Receptors, Metabotropic Glutamate / metabolism
  • Somatosensory Cortex / cytology
  • Somatosensory Cortex / physiopathology*
  • Somatostatin / metabolism
  • Synaptic Transmission / physiology
  • gamma-Aminobutyric Acid / physiology


  • Fmr1 protein, mouse
  • Receptors, Metabotropic Glutamate
  • metabotropic glutamate receptor type 1
  • Fragile X Mental Retardation Protein
  • Somatostatin
  • Methoxyhydroxyphenylglycol
  • gamma-Aminobutyric Acid
  • 3,4-dihydroxyphenylglycol