Each individual is characterized by a two-component Rayleigh distribution, which reflects two modes of movement: active movement (progression) and sedentary state (drift). A mechanical analogue would be the motion of a Brownian particle with a variable mass: small during active movement and large during drift (+ "decision-making load"). A stochastic model with random switching between these modes is constructed, which makes it possible to estimate the amount of "added mass". The experimentally obtained autocorrelation function of velocity also demonstrates two-phase attenuation with two characteristic times corresponding to the duration of progressions and the characteristic time of switching between modes.
Epigenetic rearrangements can create a favorable environment for the intrinsic plasticity of brain cells, leading to cellular reprogramming into virtually any cell type through the induction of cell-specific transcriptional programs. In this study, we assessed how chromatin remodeling induced by broad-spectrum HDAC inhibitors affects cellular differentiation trajectories in rat primary neuron–glia cultures using a combination of transcriptomics, qPCR, and cytochemistry. We described the epigenetic regulation of transcriptional programs controlled by master transcription factors and neurotrophins in the context of neuronal and glial differentiation and evaluated the expression of representative cell-specific markers. The results obtained suggest that HDAC inhibitors reduce the proliferative potential of cultured cells and induce transcriptomic changes associated with cell differentiation and specialization. Particularly, we revealed a significant upregulation of genes typically expressed in neuromodulatory neurons and the downregulation of genes expressed in glia and inhibitory neurons. Transcriptional changes were accompanied by continuous elevation of histone serotonylation levels in both neurons and glia. Emerging shortly after HDAC inhibition, a complex chromatin remodeling, which includes histone serotonylation, persists over many hours in distinct brain cells. We assume that this sustained epigenetic mechanism likely helps to maintain transcriptional changes associated with cell fate commitment, possibly priming cells for long-term fate conversion.
Neurogenic meningeal inflammation is regarded as a key driver of migraine headache. Multiple evidence show importance of inflammatory processes in the dura mater for pain generation but contribution of the leptomeninges is less clear. We assessed effects of cortical spreading depolarization (CSD), the pathophysiological mechanism of migraine aura, on expression of inflammatory mediators in the leptomeninges. A single CSD event was produced by a focal unilateral microdamage of the cortex in freely behaving rats. Three hours later intact cortical leptomeninges and parenchyma of ipsi-lesional (invaded by CSD) and sham-treated contra-lesional (unaffected by CSD) hemispheres were collected and mRNA levels of genes associated with inflammation (Il1b, Tnf, Ccl2; Cx3cl1, Zc3h12a) and endocannabinoid CB2 receptors (Cnr2) were measured using qPCR. Three hours after a single unilateral CSD, most inflammatory factors changed their expression levels in the leptomeninges, mainly on the side of CSD. The meninges overlying affected cortex increased mRNA expression of all proinflammatory cytokines (Il1b, Tnf, Ccl2) and anti-inflammatory factors Zc3h12a and Cx3cl1. Upregulation of proinflammatory cytokines was found in both meninges and parenchyma while anti-inflammatory markers increased only meningeal expression. A single CSD is sufficient to produce pronounced leptomeningeal inflammation that lasts for at least three hours and involves mostly meninges overlying the cortex affected by CSD. The prolonged post-CSD inflammation of the leptomeninges can contribute to mechanisms of headache generation following aura phase of migraine attack.
Anna Karan et al. in The Journal of Headache and Pain. Published July 2024. DOI: 10.1186/s10194-024-01823-1
https://link.springer.com/article/10.1186/s10194-024-01823-1
The role of astrocytes in modulating synaptic plasticity is an important question that until recently was not addressed due to limitations of previously existing technology. In the present study, we took an advantage of optogenetics to specifically activate astrocytes in hippocampal slices in order to study effects on synaptic function. Using the AAV-based delivery strategy, we expressed the ionotropic channelrhodopsin-2 (ChR2) or the metabotropic Gq-coupled Opto-a1AR opsins specifically in hippocampal astrocytes to compare different modalities of astrocyte activation. In electrophysiological experiments, we observed a depression of basal field excitatory postsynaptic potentials (fEPSPs) in the CA1 hippocampal layer following light stimulation of astrocytic ChR2. The ChR2-mediated depression increased under simultaneous light and electrical theta-burst stimulation (TBS). Application of the type 2 purinergic receptor antagonist suramin prevented depression of basal synaptic transmission, and switched the ChR2-dependent depression into potentiation. The GABAB receptor antagonist, phaclofen, did not prevent the depression of basal fEPSPs, but switched the ChR2-dependent depression into potentiation comparable to the values for TBS in control slices. In contrast, light stimulation of Opto-a1AR expressed in astrocytes led to an increase in basal fEPSPs, as well as a potentiation of synaptic responses to TBS significantly. A specific blocker of the Gq protein downstream target, the phospholipase C, U73122, completely prevented the effects of Opto-a1AR stimulation on basal fEPSPs or Opto + TBS responses. To understand molecular basis for the observed effects, we performed an analysis of gene expression in these slices using quantitative PCR approach. We observed a significant upregulation of “immediate-early” gene expression in hippocampal slices after light activation of Opto-a1AR-expressing astrocytes alone (cRel, Arc, Fos, JunB, and Egr1) or paired with TBS (cRel, Fos, and Egr1). Activation of ChR2-expressing hippocampal astrocytes was insufficient to affect expression of these genes in our experimental conditions. Thus, we concluded that optostimulation of astrocytes with ChR2 and Opto-a1AR optogenetic tools enables bidirectional modulation of synaptic plasticity and gene expression in hippocampus.