Biology subjects

Galanis, C.

Publications and source records attributed to Galanis, C..

10 recordsLinked to original sources

bioRxiv2026

Human cortical slices reveal pulse-number-dependent synaptic plasticity during theta-burst magnetic stimulation

Theta-burst transcranial magnetic stimulation is widely used to modulate human brain activity in clinical and experimental settings, yet how clinically relevant stimulation protocols engage synaptic plasticity in human cortical circuits remains poorly understood. Here, we combined controlled magnetic stimulation of viable adult human cortical slices with single-cell electrophysiology to determine whether pulse number constrains synaptic plasticity during intermittent theta-burst stimulation (iTBS). As a functional reference, 10 Hz repetitive magnetic stimulation delivered with 900 pulses robustly potentiated excitatory synaptic transmission in human cortical pyramidal neurons. Similarly, iTBS900 significantly potentiated AMPA receptor-mediated miniature excitatory postsynaptic currents. In contrast, the clinically established 600-pulse iTBS protocol failed to reliably induce detectable synaptic plasticity under otherwise identical stimulation conditions. Paired within-patient experiments confirmed distinct synaptic responses to iTBS600 and iTBS900 in the same human cortical tissue preparations. Together, these findings identify pulse number as an important determinant of theta-burst magnetic stimulation-induced synaptic plasticity in human cortical microcircuits and highlight stimulation dose as a relevant parameter for the design and refinement of therapeutic stimulation protocols.

neuroscience↗

bioRxiv2026

Daily repetitive magnetic stimulation induces microglia-dependent homeostatic synaptic remodeling

Therapeutic repetitive transcranial magnetic stimulation (rTMS) is delivered across repeated sessions to induce durable network-level adaptations, yet the cellular mechanisms governing these cumulative effects remain poorly understood. Using mouse organotypic brain cultures, we show that repeated daily intermittent theta burst stimulation with 900 pulses (iTBS900; 10 stimulation sessions over 2 weeks) induces a microglia-dependent adaptive synaptic response in pyramidal neurons. This response is characterized by reduced AMPAR-mediated miniature excitatory postsynaptic current (mEPSC) frequency and decreased dendritic spine density, consistent with adaptive remodeling of excitatory synaptic connectivity. Microglial depletion abolished this homeostatic response and instead resulted in increased synaptic strength and elevated spine density following repeated stimulation. Repeated daily iTBS900 also enhanced microglial uptake and degradative capacity while altering baseline and injury-induced microglial motility, indicating stimulation-dependent changes in microglial surveillance and effector functions. Together, these findings identify microglia as critical mediators of the homeostatic structural and functional adaptations induced by multi-session rTMS.

neuroscience↗

bioRxiv2024

Repetitive magnetic stimulation induces plasticity of excitatory synapses through cooperative pre- and postsynaptic activity.

Transcranial magnetic stimulation (TMS) is a widely used non-invasive technique in research and clinical settings. Despite its success, the cellular and molecular mechanisms underlying TMS-induced changes in the brain remain incompletely understood. Current protocols are largely heuristic, based on system-level observations. This study employed in vitro repetitive magnetic stimulation (rMS) in mouse brain tissue cultures, combined with computational modeling to develop an experimentally validated approach for predicting TMS effects. Unlike electrical or optogenetic stimulation, rTMS uniquely enhances plasticity by activating both pre- and postsynaptic neurons, with brain-derived neurotrophic factor (BDNF) playing a crucial role. Our simulations accurately predicted the frequency-dependent effects of rTMS, providing a critical step towards developing robust, validated tools that will enhance the precision and effectiveness of TMS applications across both research and clinical settings. Significance StatementThis study elucidates the mechanisms by which TMS promotes neural plasticity, specifically long-term potentiation (LTP) of excitatory neurotransmission. By demonstrating that rMS engages both pre- and postsynaptic neurons with BDNF as a key mediator, it provides a mechanistic basis for the therapeutic effects of rTMS. These insights advance our understanding of rTMS-induced brain plasticity and support the development of predictive computer models, paving the way for more effective and standardized TMS protocols in research and clinical applications.

neuroscience↗

bioRxiv2024

Multi-scale modelling of location- and frequency-dependent synaptic plasticity induced by transcranial magnetic stimulation in the dendrites of pyramidal neurons

BackgroundRepetitive transcranial magnetic stimulation (rTMS) induces long-term changes of synapses, but the mechanisms behind these modifications are not fully understood. Al- though there has been progress in the development of multi-scale modeling tools, no com- prehensive module for simulating rTMS-induced synaptic plasticity in biophysically realistic neurons exists.. ObjectiveWe developed a modelling framework that allows the replication and detailed prediction of long-term changes of excitatory synapses in neurons stimulated by rTMS. MethodsWe implemented a voltage-dependent plasticity model that has been previously established for simulating frequency-, time-, and compartment-dependent spatio-temporal changes of excitatory synapses in neuronal dendrites. The plasticity model can be incorporated into biophysical neuronal models and coupled to electrical field simulations. ResultsWe show that the plasticity modelling framework replicates long-term potentiation (LTP)-like plasticity in hippocampal CA1 pyramidal cells evoked by 10-Hz repetitive magnetic stimulation (rMS). This plasticity was strongly distance dependent and concentrated at the proximal synapses of the neuron. We predicted a decrease in the plasticity amplitude for 5 Hz and 1 Hz protocols with decreasing frequency. Finally, we successfully modelled plasticity in distal synapses upon local electrical theta-burst stimulation (TBS) and predicted proximal and distal plasticity for rMS TBS. Notably, the rMS TBS-evoked synaptic plasticity exhibited robust facilitation by dendritic spikes and low sensitivity to inhibitory suppression. ConclusionThe plasticity modelling framework enables precise simulations of LTP-like cellular effects with high spatio-temporal resolution, enhancing the efficiency of parameter screening and the development of plasticity-inducing rTMS protocols. HighlightsO_LIFirst rigorously validated model of TMS-induced long-term synaptic plasticity in ex- tended neuronal dendrites that goes beyond point-neuron and mean-field modelling C_LIO_LIRobust simulations of experimental data on LTP-like plasticity in the proximal dendrites of CA1 hippocampal pyramidal cells evoked by 10 Hz repetitive magnetic stimulation (rMS) C_LIO_LIReplication of distal synaptic plasticity for a local electrical theta burst stimulation (TBS) protocol C_LIO_LIPrediction of distal and proximal LTP-like plasticity for rMS TBS C_LIO_LI1 Hz rMS does not induce long-term depression C_LI

neuroscience↗

bioRxiv2024

Regional Microglial Response in Enthorino-hippocampal Slice Cultures to Schaffer Collateral Lesion and Metalloproteinases Modulation.

Microglia and astrocytes are essential in sustaining physiological networks on the central nervous system, with their ability to remodel the extracellular matrix, being pivotal for synapse plasticity. Recent findings challenge the traditional view of homogenous glial populations in the brain, uncovering morphological, functional and molecular heterogeneity among glial cells. This diversity has significant implications for both physiological and pathological brain states. In the present study, we mechanically induced a Schaffer collateral lesion (SCL) in mouse enthorino-hippocampal slice cultures to investigate glial behavior, i.e., microglia and astrocytes, under metalloproteinases (MMPs) modulation in the lesioned area, CA3, and the denervated region, CA1. We observed distinct response patterns in microglia and astrocytes 3 days after the lesion. Notably, GFAP-expressing astrocytes showed no immediate changes post-SCL. Microglia responses varied depending on their anatomical location. The MMPs inhibitor GM6001 did not affect microglial reactions in CA3, while increasing the Iba1 cells numbers in CA1, underscoring the complexity of the hippocampal neuroglial network post-injury. These findings highlight the importance of understanding glial regionalization following neural injury and MMPs modulation, and pave the way for further research into glia-targeted therapeutic strategies for neurodegenerative disorders.

neuroscience↗

bioRxiv2023

Axon morphology and intrinsic cellular properties determine repetitive transcranial magnetic stimulation threshold for plasticity

Repetitive transcranial magnetic stimulation (rTMS) is a widely used therapeutic tool in neurology and psychiatry, but its cellular and molecular mechanisms are not fully understood. Standardizing stimulus parameters, specifically electric field strength and direction, is crucial in experimental and clinical settings. It enables meaningful comparisons across studies and facilitating the translation of findings into clinical practice. However, the impact of biophysical properties inherent to the stimulated neurons and networks on the outcome of rTMS protocols remains not well understood. Consequently, achieving standardization of biological effects across different brain regions and subjects poses a significant challenge. This study compared the effects of 10 Hz repetitive magnetic stimulation (rMS) in entorhino-hippocampal tissue cultures from mice and rats, providing insights into the impact of the same stimulation protocol on similar neuronal networks under standardized conditions. We observed the previously described plastic changes in excitatory and inhibitory synaptic strength of CA1 pyramidal neurons in both mouse and rat tissue cultures, but a higher stimulation intensity was required for the induction of rMS-induced synaptic plasticity in rat tissue cultures. Through systematic comparison of neuronal structural and functional properties and computational modeling, we found that morphological parameters of CA1 pyramidal neurons alone are insufficient to explain the observed differences between the groups. However, axon morphologies of individual cells played a significant role in determining activation thresholds. Notably, differences in intrinsic cellular properties were sufficient to account for the 10 % higher intensity required for the induction of synaptic plasticity in the rat tissue cultures. These findings demonstrate the critical importance of axon morphology and intrinsic cellular properties in predicting the plasticity effects of rTMS, carrying valuable implications for the development of computer models aimed at predicting and standardizing the biological effects of rTMS.

neuroscience↗

bioRxiv2022

The amyloid precursor protein regulates synaptic transmission at medial perforant path synapses

The perforant path provides the main cortical excitatory input to the hippocampus. Due to its important role in information processing and coding, entorhinal projections to the dentate gyrus have been studied in considerable detail. Nevertheless, a characterization of synaptic transmission between individual connected pairs of entorhinal stellate cells and dentate granule cells is still pending. Here, we have used organotypic entorhino-hippocampal tissue cultures, in which the entorhino-dentate (EC-GC) projection is present and EC-GC pairs can be studied using whole-cell patch clamp recordings. Using cultures of wildtype mice, the properties of EC-GC synapses formed by afferents from the lateral and medial entorhinal cortex were compared and differences in short-term plasticity were revealed. Since the perforant path is severely affected in Alzheimers disease, we used cultures of APP-deficient mice to address the role of the amyloid-precursor protein (APP) at this synapse. APP-deficiency caused alterations in excitatory neurotransmission at medial perforant path synapses that were accompanied by transcriptomic and ultrastructural changes. Moreover, the deletion of pre- but not postsynaptic APP through the local injection of Cre-expressing AAVs in conditional APPflox/flox tissue cultures increased the efficacy of neurotransmission at perforant path synapses. Together, these data suggest a physiological role for presynaptic APP at medial perforant path synapses, which may be adversely affected under conditions of altered APP processing.

neuroscience↗

bioRxiv2021

Glby, is a PBP with β-lactamase activity and is required for in vivo viability of M. abscessus

The prevalence of Mycobacteroides abscessus, Mab, (also known as Mycobacterium abscessus) has been increasing steadily globally. Patients with structural lung conditions such as bronchiectasis, cystic fibrosis and chronic obstructive pulmonary disease are at high risk of developing pulmonary Mab disease. The disease is often recurrent as the current treatment regimen is considered sub-efficacious. The cell wall peptidoglycan of bacteria is required for their viability and its biosynthetic pathway is enriched in proteins whose inhibition is the basis for two of the most widely used classes of antibiotics to treat bacterial infections. The peptidoglycan of Mab is distinct from that of most bacteria as its synthesis involves penicillin binding proteins (PBP) and L,D-transpeptidases. Here, we demonstrate that Mab gene locus MAB_3167c encodes a PBP (hereafter referred to as Glby) and is required for normal planktonic growth in liquid broth. Glby exhibits a strong {beta}-lactamase activity and is sensitive to {beta}-lactamase inhibitors. In a mouse model of pulmonary Mab disease, mutant lacking this gene was unable to proliferate, gradually cleared and undetectable after three weeks. In a collection of 1.046 Mab clinical isolates, there is evidence that changes in amino acid sequence that compromise Glby function are not favored. These evidences suggest that an agent that can inhibit Glby in vivo has the potential to be an efficacious treatment against Mab disease.

microbiology↗

bioRxiv2020

Multi-scale Modeling Toolbox for Single Neuron and Subcellular Activity under (repetitive) Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is a non-invasive brain stimulation technique widely used in research and clinical applications. However, its mechanism of action and the neural response to TMS are still poorly understood. Multi-scale modeling can complement experimental research and provide a framework between the physical input parameters and the subcellular neural effects of TMS. At the macroscopic level, sophisticated numerical models exist to estimate the induced electric fields in whole-brain volume conductor models. However, multi-scale computational modeling approaches to predict TMS cellular and subcellular responses, crucial to understanding TMS plasticity inducing protocols, are not available so far. Here, we develop a multi-scale Neuron Modeling for TMS toolbox (NeMo-TMS) that enables researchers to easily generate accurate neuron models from morphological reconstructions, couple them to the external electric fields induced by TMS, and to simulate the cellular and subcellular responses of the neurons. Both single-pulse and rTMS protocols can be simulated and results visualized in 3D. We openly share our toolbox and provide example scripts and datasets for the user to explore. NeMo-TMS toolbox (https://github.com/OpitzLab/NeMo-TMS) allows researchers a previously not available level of detail and precision in realistically modeling the physical and physiological effects of TMS.

neuroscience↗

bioRxiv2020

Amyloid-beta mediates homeostatic synaptic plasticity

The physiological role of the amyloid-precursor protein (APP) is insufficiently understood. Recent work has implicated APP in the regulation of synaptic plasticity. Substantial evidence exists for a role of APP and its secreted ectodomain APPs in Hebbian plasticity. Here, we addressed the relevance of APP in homeostatic synaptic plasticity using organotypic tissue cultures of APP-/- mice. In the absence of APP, dentate granule cells failed to strengthen their excitatory synapses homeostatically. Homeostatic plasticity is rescued by amyloid-{beta} (A{beta}) and not by APPs, and it is neither observed in APP+/+ tissue treated with {beta}- or {gamma}-secretase inhibitors nor in synaptopodin-deficient cultures lacking the Ca2+-dependent molecular machinery of the spine apparatus. Together, these results suggest a role of APP processing via the amyloidogenic pathway in homeostatic synaptic plasticity, representing a function of relevance for brain physiology as well as for brain states associated with increased A{beta} levels.

neuroscience↗