Biology subjects

Drobyshevsky, A.

Publications and source records attributed to Drobyshevsky, A..

6 recordsLinked to original sources

bioRxiv2025

Low-frequency transcranial magnetic stimulation offers both immediate and delayed neuroprotection in neonatal hypoxia-ischemia model

Perinatal hypoxic-ischemic encephalopathy (HIE) is a leading cause of morbidity and mortality, and the current standard of care, therapeutic hypothermia, provides only partial neuroprotection. This study investigates the potential of low-frequency transcranial magnetic stimulation (LF-TMS) as a novel non-pharmacological adjunct therapy by targeting a key pathological mechanism of HIE: a persistent, pathological increase in glutamatergic synaptic transmission, or hypoxic long-term potentiation (hLTP). Using a neonatal mouse model of hypoxia-ischemia, we administered a single session of LF-TMS shortly after the hypoxic event. We then evaluated its effects on synaptic function via slice electrophysiology and on brain injury volume using serial MRI. Our results show that hypoxia-ischemia induced a significant and lasting synaptic potentiation in the brains penumbral region. A single LF-TMS treatment successfully reduced this elevated glutamatergic response to control levels, suggesting a therapeutic mechanism similar to long-term depression (LTD) by regulating AMPA receptor redistribution. Furthermore, LF-TMS provided significant neuroprotection, as demonstrated by a reduction in the volume of the ischemic core and penumbra 48 hours after the injury. LF-TMS did not alter excitability in sham-treated mice, confirming its safety as a targeted intervention for pathological conditions without affecting normal brain function. This study provides strong evidence that LF-TMS is a promising neuroprotective strategy that acutely and subacutely mitigates brain injury in a neonatal hypoxia-ischemia model.

neuroscience↗

bioRxiv2025

Comparative Analysis of Neonatal Hypomyelination Models Using Spatial Transcriptomics

White matter injury (WMI) is a major cause of morbidity in premature infants, contributing to 5%-10% of cerebral palsy cases and up to 50% of cognitive and behavioral deficits in the United States. Two commonly used preclinical models, intermittent hypoxia (IH) and hypoxia-ischemia (HI) are widely employed to investigate the effects of WMI. The internal capsule (IC) and corpus callosum (CC) are major white matter tracts undergoing active myelination during the neonatal period, making them particularly vulnerable to hypoxic insults. This study aims to compare the effects of IH and HI models on myelination as well as the involvement of inflammatory cells in the IC and CC. We evaluated five oligodendrocyte (OL) subtypes, along with astrocytes, microglia, and activated microglia in IC and CC at postnatal day 12 (P12) and day 20 (P20) using spatial transcriptomics (CosMx, Novogene). For the HI model, C57BL/6 mice at P10 underwent permanent ligation of the left carotid artery followed by 45 minutes of hypoxia (8% O2 / 92% N2). For the IH model, P3 mice were exposed to 5% O2 / 95% N2, twice daily for five consecutive days. Animals were euthanized at P12 and P20, perfused transcardially, and brains were post-fixed in 4% paraformaldehyde, dehydrated in an ethanol series, embedded in paraffin, and coronally sectioned at 7 m. Slides were submitted for CosMx spatial transcriptomic analysis (NanoString Technologies), and data analysis was performed using the Seurat package in RStudio. Our results demonstrate that IH and HI models affect OL populations differently, and these effects vary by brain region. In the IC, the IH model caused earlier and more pronounced changes in OL differentiation-related gene expression compared to HI. In contrast, the CC was more affected by HI. Moreover, in the HI group, mature OL s in both regions showed reduced expression of myelination-associated genes. This was accompanied by greater activation of inflammatory cells and increased intercellular communication between these cells and mature OLs, potentially contributing to the observed hypomyelination. Overall, our study provides critical insights into how each model of neonatal hypoxia differentially impacts white matter development. This knowledge can help refine preclinical strategies and guide therapeutic research tailored to the underlying pathology of each model.

neuroscience↗

bioRxiv2025

Differential effect of low and high frequency transcranial magnetic stimulation on cortical excitability and myelination after neonatal hypoxia in mice

Premature infants are highly prone to intermittent hypoxic brain injury, which is linked to adverse motor, cognitive, and behavioral outcomes, including attention deficits, hyperactivity, and learning difficulties. Previous animal studies have revealed myelination deficits and increased glutamatergic synaptic strength in the sensory-motor cortex. This study examines the feasibility, safety, and therapeutic potential of repetitive transcranial magnetic stimulation (rTMS) to improve central hypomyelination, reduce excessive glutamatergic transmission in cortical neurons after neonatal intermittent hypoxia (IH), and enhance behavioral outcomes. In a mouse model of neonatal IH brain injury, low-frequency (LF-rTMS) at 1 Hz or high-frequency (HF-rTMS) at 10 Hz was administered for 5 days shortly after the injury. The rTMS treatment did not cause apoptosis or inflammation. HF-rTMS notably ameliorated hypomyelination in the corticospinal tract in both the stimulated and non-stimulated hemispheres. LF-rTMS decreased hyperactivity in female IH mice and lowered the heightened glutamatergic synaptic excitability in motor cortex slices. The data suggest that rTMS can affect both myelination and synaptic excitability, leading to improved behavioral outcomes following neonatal hypoxic brain injury. These results support the potential of rTMS as an early intervention for neurological issues caused by perinatal hypoxia.

neuroscience↗

bioRxiv2024

Abnormal local cortical functional connectivity due to interneuron dysmaturation after neonatal intermittent hypoxia

BackgroundPremature infants often experience frequent hypoxic episodes due to immaturity of respiratory control that may result in disturbances of gray and white matter development and long-term cognitive and behavioral abnormalities. We hypothesize that neonatal intermittent hypoxia alters cortical maturation of excitatory and inhibitory circuits that can be detected early with functional MRI. MethodsC57BL/6 mouse pups were exposed to an intermittent hypoxia (IH) regimen consisting of 12 to 20 daily hypoxic episodes of 5% oxygen exposure for 2 min at 37C from P3 to P7, followed by MRI at P12 and electrophysiological recordings in cortical slices and in vivo at several time points between P7 and P13. Behavioral tests were conducted at P41-P50 to assess animal activity and motor learning. ResultsAdult mice after neonatal IH exhibited hyperactivity in open field test and impaired motor learning in complex wheel tasks. Patch clamp and evoked field potential electrophysiology revealed increased glutamatergic transmission accompanied by elevation of tonic inhibition. A decreased synaptic inhibitory drive was evidenced by miniature IPSC frequency on pyramidal cells, multi-unit activity recording in vivo in the motor cortex with selective GABAA receptor inhibitor picrotoxin injection, as well as by the decreased interneuron density at P13. There was also an increased tonic depolarizing effect of picrotoxin after IH on principal cells membrane potential on patch clamp and direct current potential in extracellular recordings. The amplitude of low-frequency fluctuation on resting-state fMRI was larger, with a larger increase after picrotoxin injection in the IH group. ConclusionsIncreased excitatory glutamatergic transmission, decreased numbers, and activity of inhibitory interneurons after neonatal IH may affect the maturation of connectivity in cortical networks, resulting in long-term cognitive and behavioral changes, including impaired motor learning and hyperactivity. Functional MRI reveals increased intrinsic connectivity in the sensorimotor cortex, suggesting neuronal dysfunction in cortical maturation after neonatal IH. The increased tonic inhibition, presumably due to tonic extrasynaptic GABA receptor drive, may be compensatory to the elevated excitatory glutamatergic transmission.

neuroscience↗

bioRxiv2023

Spinal motoneurons respond aberrantly to serotonin in a rabbit model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors that damage the developing central nervous system. Impaired motor control, including muscle stiffness and spasticity, is the hallmark of spastic CP. Rabbits that experience hypoxic-ischemic (HI) injury in utero (at 70-80% gestation) are born with muscle stiffness, hyperreflexia, and, as recently discovered, increased serotonin (5-HT) in the spinal cord. To determine whether serotonergic modulation of spinal motoneurons (MNs) contributes to motor deficits, we performed ex vivo whole cell patch clamp in neonatal rabbit spinal cord slices at postnatal day (P) 0-5. HI MNs responded to application of -methyl 5-HT (a 5-HT1/5-HT2 receptor agonist) and citalopram (a selective 5-HT reuptake inhibitor) with hyperpolarization of persistent inward currents and threshold voltage for action potentials, reduced maximum firing rate, and an altered pattern of spike frequency adaptation while control MNs did not exhibit any of these responses. To further explore the differential sensitivity of MNs to 5-HT, we performed immunohistochemistry for inhibitory 5-HT1A receptors in lumbar spinal MNs at P5. Fewer HI MNs expressed the 5-HT1A receptor compared to age-matched controls. This suggests many HI MNs lack a normal mechanism of central fatigue mediated by 5-HT1A receptors. Other 5-HT receptors (including 5-HT2) are likely responsible for the robust increase in HI MN excitability. In summary, by directly exciting MNs, the increased concentration of spinal 5-HT in HI rabbits can cause MN hyperexcitability, muscle stiffness, and spasticity characteristic of CP. Therapeutic strategies that target serotonergic neuromodulation may be beneficial to individuals with CP. Key pointsO_LIAfter prenatal hypoxia-ischemia (HI), neonatal rabbits that show hypertonia are known to have higher levels of spinal serotonin C_LIO_LIWe tested responsivity of spinal motoneurons (MNs) in neonatal control and HI rabbits to serotonin using whole cell patch clamp C_LIO_LIMNs from HI rabbits showed a more robust excitatory response to serotonin than control MNs, including hyperpolarization of the persistent inward current and threshold for action potentials, larger post-inhibitory rebound, and less spike frequency adaptation C_LIO_LIBased on immunohistochemistry of lumbar MNs, fewer HI MNs express inhibitory 5HT1A receptors than control MNs, which could account for the more robust excitatory response of HI MNs. C_LIO_LIThese results suggest that after HI injury, the increased serotonin could trigger a cascade of events leading to muscle stiffness and altered motor unit development C_LI

neuroscience↗

bioRxiv2019

Altered motoneuron properties and spinal serotonin contribute to motor deficits in a rabbit hypoxia ischemia model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors attributed to early brain damage, resulting in permanently impaired motor control, marked by weakness and muscle stiffness. To find out if altered physiology of spinal motoneurons (MNs) could contribute to movement deficits, we performed whole cell patch clamp in neonatal rabbit spinal cord slices after developmental injury at 79% gestation. After preterm hypoxia-ischemia (HI), rabbits are born with motor deficits consistent with a spastic phenotype including hypertonia and hyperreflexia. There is a range in severity, thus kits are classified as severely affected, mildly affected, or unaffected based on modified Ashworth scores and other behavioral tests. At postnatal day (P)0-5, we recorded electrophysiological parameters of 40 MNs in transverse spinal cord slices using whole cell patch clamp. Using a multivariate analysis of neuronal parameters, we found significant differences between groups (severe, mild, unaffected and sham control MNs), age (P0 to P5) and spinal cord region (cervical to sacral). Severe HI MNs showed more sustained firing patterns, depolarized resting membrane potential, and a higher threshold for action potentials. These properties could contribute to both muscle stiffness and weakness, respectively, hallmarks of spastic CP. Interestingly altered persistent inward currents (PICs) and morphology in severe HI MNs would dampen excitability (reduced normalized PIC amplitude and increased dendritic length). In summary, changes we observed in spinal MN physiology likely contribute to severity of the phenotype including weakness and hypertonia, and therapeutic strategies for CP could target excitability of spinal MNs. Key PointsO_LIPhysiology of neonatal spinal motoneurons is altered after in utero hypoxia-ischemic injury C_LIO_LIIn motoneurons from severely affected animals there is more sustained firing (lower {Delta}I values), a depolarized resting potential, but a higher voltage threshold for action potential firing. C_LIO_LIAltered motoneuron excitability could contribute directly to muscle stiffness and spasticity in cerebral palsy. C_LI

neuroscience↗