Biology subjects

Lau, L. A.

Publications and source records attributed to Lau, L. A..

3 recordsLinked to original sources

bioRxiv2026

Robust Induction of Spontaneous Recurrent Seizures and Hippocampal Sclerosis with Synthetic Kainic Acid in the Intrahippocampal Kainate Model

Intrahippocampal kainate (IHK) is a well-established mouse model of temporal lobe epilepsy, in which focal hippocampal injection of kainic acid induces excitotoxic injury followed by the development of chronic spontaneous seizures. Commercial sources of kainic acid (KA) have increasingly transitioned from naturally derived to synthetic KA, which has introduced a potential source of variability to the implementation of the IHK model. Here, we evaluated injection parameters for synthetic KA, with the goal of identifying conditions that reliably produce spontaneous seizures while minimizing mortality. We found that intrahippocampal injection of 200nL of 5mM synthetic KA resulted in low mortality compared to 50-100nL of 20mM synthetic KA (a dosing range commonly used with naturally derived KA), while robustly inducing TLE-like hippocampal sclerosis and recurrent spontaneous electroclinical seizures. We further demonstrated high inter-animal variability in both seizure frequency and temporal clustering of seizures across animals receiving either injection protocol (200nL of 5mM or 50nL of 20mM). Together, these findings provide a framework for implementing the IHK model with synthetic KA and support its continued use to advance our understanding of the cellular and network mechanisms underlying temporal lobe epilepsy.

neuroscience↗

bioRxiv2024

Ongoing loss of viable neurons for weeks after mild perinatal hypoxia-ischemia

Mild hypoxic-ischemic encephalopathy is common in neonates with no evidence-based therapies, and 30-40% of patients experience adverse outcomes. The nature and progression of mild injury is poorly understood. Thus, we studied the evolution of mild perinatal brain injury using longitudinal two-photon imaging of transgenic fluorescent proteins as a novel readout of neuronal viability and activity at cellular resolution. In vitro, perinatal murine organotypic hippocampal cultures underwent 15-20 minutes of oxygen-glucose deprivation. In vivo, mild hypoxia-ischemia was completed in post-natal day 10 mouse pups of both sexes with carotid ligation and 15 minutes of hypoxia. Consistent with a mild injury, minimal immediate neuronal death was seen and there was no volumetric evidence of injury by ex vivo MRI 2.5 weeks after injury. In both the hippocampus and neocortex, these mild injuries resulted in a significantly delayed and progressive neuronal loss in the second week after injury, measured by fluorophore quenching. Mild hypoxia-ischemia transiently suppressed cortical network activity followed by normal maturation. No post-injury seizures were seen. The participation in network activity of individual neurons destined to die was indistinguishable from those that survived for 4 days post-injury. In conclusion, our results showed that mild perinatal brain injury resulted in a prolonged increase of neuronal death. Neurons that died late were functioning normally for days after injury, suggesting a new pathophysiology of neuronal death. Critically, the neurons destined to die late demonstrated multiple biomarkers of viability long after mild injury, suggesting their later death may be modified with neuroprotective interventions. SIGNIFICANCE STATEMENTNeonatal encephalopathy due to peripartum hypoxia-ischemia (HI) is a major cause of neonatal mortality and morbidity worldwide. Of these infants, most are categorized as having mild HI. Infants with mild HI have significant long-term disabilities. There are currently no evidence-based therapies, largely because the progression and pathophysiology of mild injury is poorly understood. We have identified, for the first time, that mild perinatal HI results in a delayed and prolonged increase in neuronal death. The cortical and hippocampal neurons that die over a week after injury participate normally in neural network activity and exhibit robust viability for many days after injury, indicating a novel pathophysiology of neuronal death. Clinically, these data suggest an extended therapeutic window for mild perinatal HI.

neuroscience↗

bioRxiv2022

Cellular contributions to ictal population signals

ObjectiveThe amplitude of ictal activity is a defining feature of epileptic seizures, but the determinants of this amplitude have not been identified. Clinically, ictal amplitudes are measured electrographically (using e.g. EEG, ECoG, and depth electrodes), but these methods do not enable the assessment of the activity of individual neurons. To identify the cellular determinants of the ictal signal, we measured single cell and population electrical activity and neuronal calcium levels via optical imaging of the genetically encoded calcium indicator (GECI) GCaMP. MethodsSpontaneous seizure activity was assessed in an awake, behaving mouse model of focal cortical injury and in organotypic hippocampal slice cultures (OHSC), an in vitro preparation from which recurrent seizures can be readily captured. Single cell calcium signals were linked to a range of electrical activities by performing simultaneous GECI-based calcium imaging and whole-cell patch-clamp recordings in spontaneously seizing OHSCs. Neuronal resolution calcium imaging was then performed during spontaneous seizures in vivo and in vitro to quantify the cellular contributions to the population-level calcium signal. ResultsPopulation signal may increase from three potential sources: 1) increased synchrony, i.e. more co-active neurons, 2) altered active state, from bursts of action potentials and/or paroxysmal depolarizing shifts in membrane potential, and 3) altered subthreshold state, which includes all lower levels of activity. The largest contributor to the signal recorded at seizure onset was increased subthreshold activity, consistent with either barrages of excitatory postsynaptic potentials or sustained membrane depolarization. The relative contribution of synchrony increased as seizures progressed, but cell intrinsic alterations in both the subthreshold and active states remained the largest driver of the ictal signal. SignificanceWe introduce here a novel method for the quantification of the relative contributions of inter-versus intra-cellular changes to provide a critical link between single neuron activity and population measures of seizure activity. Key PointsO_LINeuronal calcium as measured by GCaMP reports a range of membrane depolarizations, from EPSPs to action potential firing and paroxysmal depolarizing shifts C_LIO_LIThe mean population calcium signal is highly correlated with the electrographic local field potential C_LIO_LIIncreased calcium signal during seizure onset is largely driven by increased subthreshold calcium within individual neurons C_LIO_LIRecruitment of newly active neurons is a minor contributor to the increasing population-level signal during the transition to frank seizure C_LI

neuroscience↗