Ictal activity is sustained by the estrogen receptor ß during the estrous cycle.

Catamenial epilepsy, defined as a periodicity of seizure exacerbation during the menstrual cycle, affects up to 70 % of epileptic women. Seizures in these patients are often non-responsive to medication; however, our understanding of the relation between menstrual cycle and seizure generation (i.e. ictogenesis) remains limited. We employed here field potential recordings in the in vitro 4-aminopyridine model of epileptiform synchronization in female mice (P60-P130) and found that: (i) the estrous phase favors ictal activity in the entorhinal cortex; (ii) these ictal discharges display an onset pattern characterised by the presence of chirps that are thought to mirror synchronous interneuron firing; and (iii) blocking estrogen receptor ß-mediated signaling reduces ictal discharge duration. Our findings indicate that the duration of 4AP-induced ictal discharges, in vitro, increases during the estrous phase, which corresponds to the human peri-ovulatory period. We propose that these effects are caused by the presumptive enhancement of interneuron excitability due to increased estrogen receptor ß-mediated signaling.

The p75 Neurotrophin Receptor in Preadolescent Prefrontal Parvalbumin Interneurons Promotes Cognitive Flexibility in Adult Mice.

BACKGROUND: Parvalbumin (PV)-positive GABAergic (gamma-aminobutyric acidergic) cells provide robust perisomatic inhibition to neighboring pyramidal neurons and regulate brain oscillations. Alterations in PV interneuron connectivity and function in the medial prefrontal cortex have been consistently reported in psychiatric disorders associated with cognitive rigidity, suggesting that PV cell deficits could be a core cellular phenotype in these disorders. The p75 neurotrophin receptor (p75NTR) regulates the time course of PV cell maturation in a cell-autonomous fashion. Whether p75NTR expression during postnatal development affects adult prefrontal PV cell connectivity and cognitive function is unknown. METHODS: We generated transgenic mice with conditional knockout of p75NTR in postnatal PV cells. We analyzed PV cell connectivity and recruitment following a tail pinch by immunolabeling and confocal imaging in naïve mice or following p75NTR re-expression in preadolescent or postadolescent mice using Cre-dependent viral vectors. Cognitive flexibility was evaluated using behavioral tests. RESULTS: PV cell-specific p75NTR deletion increased both PV cell synapse density and proportion of PV cells surrounded by perineuronal nets, a marker of mature PV cells, in adult medial prefrontal cortex, but not visual cortex. Both phenotypes were rescued by viral-mediated reintroduction of p75NTR in preadolescent, but not postadolescent, medial prefrontal cortex. Prefrontal cortical PV cells failed to upregulate c-Fos following a tail-pinch stimulation in adult conditional knockout mice. Finally, conditional knockout mice showed impaired fear memory extinction learning as well as deficits in an attention set-shifting task. CONCLUSIONS: These findings suggest that p75NTR expression in adolescent PV cells contributes to the fine-tuning of their connectivity and promotes cognitive flexibility in adulthood.

Detecting fine and elaborate movements with piezo sensors provides non-invasive access to overlooked behavioral components.

Behavioral phenotyping devices have been successfully used to build ethograms, but many aspects of behavior remain out of reach of available phenotyping systems. We now report on a novel device, which consists in an open-field platform resting on highly sensitive piezoelectric (electromechanical) pressure-sensors, with which we could detect the slightest movements (up to individual heart beats during rest) from freely moving rats and mice. The combination with video recordings and signal analysis based on time-frequency decomposition, clustering, and machine learning algorithms provided non-invasive access to previously overlooked behavioral components. The detection of shaking/shivering provided an original readout of fear, distinct from but complementary to behavioral freezing. Analyzing the dynamics of momentum in locomotion and grooming allowed to identify the signature of gait and neurodevelopmental pathological phenotypes. We believe that this device represents a significant progress and offers new opportunities for the awaited advance of behavioral phenotyping.

Sensory processing dysregulations as reliable translational biomarkers in SYNGAP1 haploinsufficiency.

Amongst the numerous genes associated with intellectual disability, SYNGAP1 stands out for its frequency and penetrance of loss-of-function variants found in patients, as well as the wide range of co-morbid disorders associated with its mutation. Most studies exploring the pathophysiological alterations caused by Syngap1 haploinsufficiency in mouse models have focused on cognitive problems and epilepsy; however, whether and to what extent sensory perception and processing are altered by Syngap1 haploinsufficiency is less clear. By performing EEG recordings in awake mice, we identified specific alterations in multiple aspects of auditory and visual processing, including increased baseline gamma oscillation power, increased theta/gamma phase amplitude coupling following stimulus presentation and abnormal neural entrainment in response to different sensory modality-specific frequencies. We also report lack of habituation to repetitive auditory stimuli and abnormal deviant sound detection. Interestingly, we found that most of these alterations are present in human patients as well, thus making them strong candidates as translational biomarkers of sensory-processing alterations associated with SYNGAP1/Syngap1 haploinsufficiency.

Potential Involvement of Impaired BKCa Channel Function in Sensory Defensiveness and Some Behavioral Disturbances Induced by Unfamiliar Environment in a Mouse Model of Fragile X Syndrome.

In fragile X syndrome (FXS), sensory hypersensitivity and impaired habituation is thought to result in attention overload and various behavioral abnormalities in reaction to the excessive and remanent salience of environment features that would normally be ignored. This phenomenon, termed sensory defensiveness, has been proposed as the potential cause of hyperactivity, hyperarousal, and negative reactions to changes in routine that are often deleterious for FXS patients. However, the lack of tools for manipulating sensory hypersensitivity has not allowed the experimental testing required to evaluate the relevance of this hypothesis. Recent work has shown that BMS-204352, a BKCa channel agonist, was efficient to reverse cortical hyperexcitability and related sensory hypersensitivity in the Fmr1-KO mouse model of FXS. In the present study, we report that exposing Fmr1-KO mice to novel or unfamiliar environments resulted in multiple behavioral perturbations, such as hyperactivity, impaired nest building and excessive grooming of the back. Reversing sensory hypersensitivity with the BKCa channel agonist BMS-204352 prevented these behavioral abnormalities in Fmr1-KO mice. These results are in support of the sensory defensiveness hypothesis, and confirm BKCa as a potentially relevant molecular target for the development of drug medication against FXS/ASD.