Biology subjects

Gallagher, M. J.

Publications and source records attributed to Gallagher, M. J..

4 recordsLinked to original sources

bioRxiv2023

Preoptic area controls sleep-related seizure onset in a genetic epilepsy mouse model

In genetic and refractory epileptic patients, seizure activity exhibits sleep-related modulation/regulation and sleep and seizure are intermingled. In this study, by using one het Gabrg2Q390X KI mice as a genetic epilepsy model and optogenetic method in vivo, we found that subcortical POA neurons were active within epileptic network from the het Gabrg2Q390XKI mice and the POA activity preceded epileptic (poly)spike-wave discharges(SWD/PSDs) in the het Gabrg2Q390X KI mice. Meanwhile, as expected, the manipulating of the POA activity relatively altered NREM sleep and wake periods in both wt and the het Gabrg2Q390X KI mice. Most importantly, the short activation of epileptic cortical neurons alone did not effectively trigger seizure activity in the het Gabrg2Q390X KI mice. In contrast, compared to the wt mice, combined the POA nucleus activation and short activation of the epileptic cortical neurons effectively triggered or suppressed epileptic activity in the het Gabrg2Q390X KI mice, indicating that the POA activity can control the brain state to trigger seizure incidence in the het Gabrg2Q390X KI mice in vivo. In addition, the suppression of POA nucleus activity decreased myoclonic jerks in the Gabrg2Q390XKI mice. Overall, this study discloses an operational mechanism for sleep-dependent seizure incidence in the genetic epilepsy model with the implications for refractory epilepsy. This operational mechanism also underlies myoclonic jerk generation, further with translational implications in seizure treatment for genetic/refractory epileptic patients and with contribution to memory/cognitive deficits in epileptic patients.

neuroscience↗

bioRxiv2022

An Open-Source Rodent Chronic EEG Array System with High Density MXene-Based Skull Surface Electrodes

Electroencephalography (EEG) is an indispensable tool in epilepsy, sleep, and behavioral research. In rodents, EEG recordings are typically performed with metal electrodes that traverse the skull into the epidural space. In addition to requiring a major surgery, this intracranial EEG technique is difficult to perform for more than a few electrodes, is time-intensive, and confounds experiments studying traumatic brain injury. Here, we describe an open-source cost-effective refinement of this technique for chronic mouse EEG recording. Our alternative two channel (EEG2) and sixteen channel high-density EEG (HdEEG) arrays use electrodes made of the novel, flexible 2D nanomaterial titanium carbide (Ti3C2Tx) MXene. The MXene electrodes are placed on the surface of the intact skull and establish electrical connection without conductive gel or paste. Fabrication and implantation times of MXene EEG electrodes are significantly shorter than the standard approach and recorded resting baseline and epileptiform EEG waveforms are similar to those obtained with traditional epidural electrodes. Applying HdEEG to a mild traumatic brain injury (mTBI) model in mice of both sexes revealed that mTBI significantly altered awake resting state spectral density with a spatiospectral region of interest in the {beta} spectral band (12-30 Hz) in the central and posterior regions. These findings indicate that fabrication of MXene electrode arrays is a cost effective, efficient technology for multichannel EEG recording in rodents that obviates the need for skull-penetrating surgery. Moreover, increased {beta} spectral power may contribute to the development of early post-mTBI seizures. Significance StatementElectroencephalography (EEG) is a critical technique used to study neurological activity in rodents. Commonly used EEG procedures require time-consuming skull-penetrating surgeries that may confound the experiments. Here we provide a cost-effective solution for obtaining two channel (EEG2) and high-density EEG (HdEEG) recordings on the skull surface thus avoiding major surgery. We compared this HdEEG system to traditional EEG recordings and then used it to determine the effects of mild traumatic brain injury on awake resting state spectral density. This novel open-source EEG system will contribute the electrophysiological characterization of rodent behaviors and seizure activity.

neuroscience↗

bioRxiv2022

Sleep slow-wave oscillations trigger seizures in a genetic epilepsy model of Dravet syndrome

Sleep is the brain state when cortical activity decreases and memory consolidates. However, in human epileptic patients, including genetic epileptic seizures such as Dravet syndrome, sleep is the preferential period when epileptic spike-wave discharges (SWDs) appear, with more severe epileptic symptoms in female patients than male patients, which influencing patient sleep quality and memory. Currently, seizure onset mechanisms during sleep period still remain unknown. Our previous work has shown that the sleep-like state-dependent synaptic potentiation mechanism can trigger epileptic SWDs(Zhang et al., 2021). In this study, using one heterozygous (het) knock-in (KI) transgenic mice (GABAA receptor {gamma}2 subunit Gabrg2Q390X mutation) and an optogenetic method, we hypothesized that slow-wave oscillations (SWOs) themselves in vivo could trigger epileptic seizures. We found that epileptic SWDs in het Gabrg2+/Q390X KI mice exhibited preferential incidence during NREM sleep period, accompanied by motor immobility/ facial myoclonus/vibrissal twitching, with more frequent incidence in female het KI mice than male het KI mice. Optogenetic induced SWOs in vivo significantly increased epileptic seizure incidence in het Gabrg2+/Q390X KI mice with increased duration of NREM sleep or quiet-wakeful states. Furthermore, suppression of SWO-related homeostatic synaptic potentiation by 4- (diethylamino)-benzaldehyde (DEAB) injection (i.p.) greatly decreased seizure incidence in het KI mice, suggesting that SWOs did trigger seizure activity in het KI mice. In addition, EEG delta-frequency (0.1-4 Hz) power spectral density during NREM sleep was significantly larger in female het Gabrg2+/Q390X KI mice than male het Gabrg2+/Q390X KI mice, which likely contributes to the gender difference in seizure incidence during NREM sleep/quiet-wake as that in human patients.

neuroscience↗

bioRxiv2020

Impaired state-dependent potentiation of GABAergic synaptic currents triggers seizures in an idiopathic generalized epilepsy model

Idiopathic generalized epilepsy(IGE) patients have genetic causes and their seizure onset mechanisms particularly during sleep remain elusive. Here we proposed that sleep-like slow-wave oscillations(0.5 Hz SWOs) potentiated excitatory or inhibitory synaptic currents in layer V cortical pyramidal neurons from wild-type(wt) mouse ex vivo brain slices. In contrast, SWOs potentiated excitatory, not inhibitory, currents in cortical neurons from heterozygous(het) knock-in(KI) IGE mice(GABAA receptor {gamma}2 subunit Gabrg2Q390X mutation), creating an imbalance between evoked excitatory and inhibitory currents to effectively prompt neuronal action potentials. Similarly, more physiologically similar up/down-state(present during slow-wave sleep) induction in cortical neurons could potentiate excitatory synaptic currents within slices from wt/het Gabrg2Q390X KI mice. Consequently, SWOs or up/down-state induction in vivo (using optogenetic method) could trigger epileptic spike-wave discharges(SWDs) in het Gabrg2Q390X KI mice. To our knowledge, this is the first operative mechanism to explain why epileptic SWDs preferentially happen during non-REM sleep or quiet-wakefulness in human IGE patients.

neuroscience↗