Biology subjects

Aksenov, D.

Publications and source records attributed to Aksenov, D..

3 recordsLinked to original sources

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↗

bioRxiv2020

European Primary Forest Database (EPFD) v2.0

Primary forests are scarce in Europe and continue to disappear at an alarming rate. Despite these losses, we know little about where such forests still occur. Here, we present an updated geodatabase and map of Europes known primary forests. Our geodatabase harmonizes 48 different datasets of primary forests, and contains 18,411 individual patches (41.1 Mha) spread across 33 countries. When available, we provide information on each patch (name, location, naturalness, extent and dominant tree species) and the surrounding landscape (biogeographical regions, protection status, potential natural vegetation, current forest extent). To assess the robustness of our geodatabase, we checked each patch for forest disturbance events using Landsat satellite-image time series (1985-2018). We estimate that 94% of the patches in our database did not experience significant disturbances that would alter their primary forest status in the last 30 year. Our database is the most comprehensive dataset on primary forests in Europe, and will be useful for biogeographic and ecological studies, and conservation planning to safeguard these unique forests.

ecology↗