# Combined Treatment with Minocycline and an mGluR5 Antagonist Alters Resting EEG Spectral Power, but Not Sound-Evoked Responses, in a Mouse Model of Fragile X Syndrome

## TL;DR

A combination of minocycline and an mGluR5 antagonist reduced abnormal brain activity in a mouse model of Fragile X Syndrome, but had no effect on sound-evoked responses.

## Contribution

A novel combination therapy targeting mGluR5 and MMP-9 was tested for its effects on EEG in a mouse model of FXS.

## Key findings

- Combined CTEP and minocycline reduced resting gamma band power in Fmr1 KO mice.
- CTEP alone had no significant effect on EEG measures in Fmr1 KO mice.
- No changes were observed in sound-evoked EEG responses with the treatments.

## Abstract

Fragile X Syndrome (FXS) is a leading genetic cause of intellectual disability and autism-like behaviors. Glutamatergic mGluR5 receptors and matrix metalloproteinase-9 (MMP-9) are therapeutic targets to treat FXS, but clinical trials targeting each of these pathways have not been successful. Here, we tested if the electroencephalography (EEG) phenotypes associated with FXS are reversed with a novel combination of treatments affecting the two pathways. Fmr1 knockout (KO) mice were given 10 days of CTEP (mGluR5 antagonist) alone or in combination with minocycline (MMP-9 inhibitor). EEG was recorded during resting (no acoustic stimulation) and during sound presentations (to produce sound-evoked EEG) at 1 day and 10 days after the beginning of treatment administration to test acute effects and potential tachyphylaxis. In pre-treatment WT and KO mice comparisons, we replicated previously published Fmr1 KO mouse EEG phenotypes including elevated power in the resting gamma band, elevated single trial power, and reduced phase-locking to spectrotemporally dynamic auditory stimuli. We found that CTEP treatment alone did not show any benefit compared to vehicle in Fmr1 KO mice after either 1 or 10 days of treatment. CTEP + minocycline reduced resting gamma band power in the Fmr1 KO mice to a greater extent than vehicle at both treatment time points. There were no effects on sound-evoked responses. These data suggest that combined CTEP and minocycline treatment alters resting EEG measures while each treatment administered separately does not yield similar changes. High power in broadband gamma frequency correlates with irritability, stereotyped behaviors, and hyperactivity in FXS patients, suggesting a combination of drugs that reduce mGluR5 and MMP-9 activity may be beneficial in FXS.