Sound processing in the cricket brain: evidence for a pulse duration filter.

The auditory system of female crickets allows them to specifically recognize and approach the species-specific male calling song, defined by sound pulses and silent intervals. Auditory brain neurons form a delay-line and coincidence detector network tuned to the pulse period of the male song. We analyzed the impact of changes in pulse duration on the behavior and the responses of the auditory neurons and the network. We confirm that the ascending neuron AN1 and the local neuron LN2 copy the temporal structure of the song. During ongoing long sound pulses, the delay-line neuron LN5 shows additional rebound responses and the coincidence detector neuron LN3 can generate additional bursts of activity, indicating that these may be driven by intrinsic oscillations of the network. Moreover, the response of the feature detector neuron LN4 is shaped by a combination of inhibitory and excitatory synaptic inputs, and LN4 responds even to long sound pulses with a short depolarization and burst of spikes, like to a sound pulse of natural duration. This response property of LN4 indicates a selective auditory pulse duration filter mechanism of the pattern recognition network, which is tuned to the duration of natural pulses. Comparing the tuning of the phonotactic behavior with the tuning of the local auditory brain neurons to the same test patterns, we find no evidence that a modulation of the phonotactic behavior is reflected at the level of the feature detector neurons. This rather suggests that steering to nonattractive pulse patterns is organized at the thoracic level.NEW & NOTEWORTHY Pulse period selectivity has been reported for the cricket delay-line and coincidence detector network, whereas pulse duration selectivity is evident from behavioral tests. Pulses of increasing duration elicit responses in the pattern recognition neurons, which do not parallel the behavioral responses and indicate additional processing mechanisms. Long sound pulses elicit rhythmic rebound activity and additional bursts, whereas the feature detector neuron reveals a pulse duration filter, expanding our understanding of the pattern recognition process.

Pressure Pulsatility Links Cardio-Respiratory and Brain Rhythmicity.

This article presents evidence indicating that intracranial pressure (ICP) pulsatility, associated with the heartbeat and breathing, is not just a source of mechanical artefact in electrical recordings, but is "sensed" and plays a role in the brain's information processing. Patch-clamp recording of pressure-activated channels, and detection of Piezo2-protein channel expression in brain neurons, suggest that these channels provide neurons with an intrinsic resonance to ICP pulsatility, which acts to synchronize remote neural networks. Direct measurements in human patients indicate that heartbeat and breathing rhythms generate intracranial forces of tens of millinewtons, exceeding by orders of magnitude the localized forces shown by atomic force microscopy and optical tweezers to activate Piezo channels in isolated neocortical and hippocampal neurons. Additionally, many human touch and proprioceptors, which are also transduced by Piezo channels, show spiking that is phase-locked to heartbeat- and breathing-induced extracranial pressure pulsations. Finally, based on the observation that low-frequency oscillations modulate the phase and amplitude of high-frequency oscillations, body and brain oscillations are proposed to form a single hierarchical system in which the heartbeat is the basic frequency and scaling factor for all other oscillations. Together, these results support the idea that ICP pulsatility may be elemental in modulating the brain's electrical rhythmicity.

Pharmacological reactivation of inactive X-linked Mecp2 in cerebral cortical neurons of living mice.

Rett syndrome (RTT) is a genetic disorder resulting from a loss-of-function mutation in one copy of the X-linked gene methyl-CpG-binding protein 2 (MECP2). Typical RTT patients are females and, due to random X chromosome inactivation (XCI), ∼50% of cells express mutant MECP2 and the other ∼50% express wild-type MECP2. Cells expressing mutant MECP2 retain a wild-type copy of MECP2 on the inactive X chromosome (Xi), the reactivation of which represents a potential therapeutic approach for RTT. Previous studies have demonstrated reactivation of Xi-linked MECP2 in cultured cells by biological or pharmacological inhibition of factors that promote XCI (called "XCI factors" or "XCIFs"). Whether XCIF inhibitors in living animals can reactivate Xi-linked MECP2 in cerebral cortical neurons, the cell type most therapeutically relevant to RTT, remains to be determined. Here, we show that pharmacological inhibitors targeting XCIFs in the PI3K/AKT and bone morphogenetic protein signaling pathways reactivate Xi-linked MECP2 in cultured mouse fibroblasts and human induced pluripotent stem cell-derived postmitotic RTT neurons. Notably, reactivation of Xi-linked MECP2 corrects characteristic defects of human RTT neurons including reduced soma size and branch points. Most importantly, we show that intracerebroventricular injection of the XCIF inhibitors reactivates Xi-linked Mecp2 in cerebral cortical neurons of adult living mice. In support of these pharmacological results, we also demonstrate genetic reactivation of Xi-linked Mecp2 in cerebral cortical neurons of living mice bearing a homozygous XCIF deletion. Collectively, our results further establish the feasibility of pharmacological reactivation of Xi-linked MECP2 as a therapeutic approach for RTT.

Azadirachtin directly or indirectly affects the abundance of intestinal flora of Spodoptera litura and the energy conversion of intestinal contents mediates the energy balance of intestine-brain axis, and along with decreased expression CREB in the brain neurons.

Azadirachtin is a good growth inhibitor for Lepidopteran larvae, but its effect on the brain neurons, intestinal flora and intestinal contents caused by the growth inhibition mechanism has not been reported yet. This study explored the mechanism of azadirachtin on the growth and development of Spodoptera litura larvae and brain neurons through three aspects: intestinal pathology observation, intestinal flora sequencing, and intestinal content analysis. The results showed that the treatment of azadirachtin led to the pathological changes in the structure of the midgut and the goblet cells in the intestinal wall cells to undergo apoptosis. Changes in the host environment of the intestinal flora lead to changes in the abundance value of the intestinal flora, showing an increase in the abundance value of harmful bacteria such as Sphingomonas and Enterococcus, as well as an increase in the abundance value of excellent flora such as Lactobacillus and Bifidobacterium. Changes in the abundance of intestinal flora will result in changes in intestinal contents and metabolites. The test results show that after azadirachtin treatment, the alkane compounds in the intestinal contents of the larvae are greatly reduced, and the number of the long carbon chain and multi-branched hydrocarbon compounds is increased, unsaturated fatty acids, silicon­oxygen compounds and ethers. The production of similar substances indicates that azadirachtin has an inhibitory effect on digestive enzymes in the intestines, which results in the inhibition of substance absorption and energy transmission, and ultimately the inhibition of larval growth and brain neurons.

Reaction of different cell types of the brain on neurotoxin cuprizone and hormone melatonin treatment in young and aging mice.

Introduction: The brain myelin and neurons destruction in multiple sclerosis may be associated with the production of neuroinflammatory cells (macrophages, astrocytes, T-lymphocytes) of pro-inflammatory cytokines and free radicals. The age-associated changes of the above cells can influence on the response of nervous system cells to toxic damaging and regulatory factors of humoral/endocrine nature, in particular pineal hormone melatonin. The study aim was (1) to evaluate changes of the brain macrophages, astrocytes, T-cells, neural stem cells, neurons, and central nervous system (CNS) functioning in the neurotoxin cuprizone-treated mice of different age; and (2) to assess in such mice the effects of exogenous melatonin and possible courses of its action. Methods: A toxic demyelination and neurodegeneration model was induced in 129/Sv mice aged 3-5 and 13-15 months by adding cuprizone neurotoxin to their food for 3 weeks. From the 8th day of the cuprizone treatment, melatonin was injected intraperitoneally at 6 p.m. daily, at a dose of 1 mg/kg. The brain GFPA + -cells were evaluated by immunohistochemical method, the proportion of CD11b+, CD3+CD11b+, CD3+, CD3+CD4+, CD3+CD8+, Nestin+-cells was determined via flow cytometry. Macrophage activity was evaluated by their ability to phagocytose latex beads Morphometric analysis of the brain neurons and the behavioral reactions ("open field" and rotarod tests) were performed. To assess the involvement of the bone marrow and thymus in the action of melatonin, the amount of granulocyte/macrophage colony-forming cells (GM-CFC), and blood monocytes and thymic hormone thymulin were evaluated. Results and discussion: The numbers of the GFAP+-, CD3+-, CD3+CD4+, CD3+CD8+, CD11b+, CD3+CD11b+, Nestin+-cells and macrophages phagocytic latex beads and malondialdehyde (MDA) content were increased in the brain of young and aging mice under cuprizone influence. The proportion of undamaged neurons within the brain, motor, affective, and exploratory activities, and muscle tone decreased in mice of both ages. Introducing melatonin to mice of any age reduced the number of GFAP+-, CD3+- cells and their subpopulations, macrophage activation, and MDA content. At the same time, the percentage of brain neurons that were unchanged increased as the number of Nestin+ cells decreased. The behavioral responses were also improved. Besides, the number of bone marrow GM-CFC and the blood level of monocytes and thymulin increased. The effects of both neurotoxin and melatonin on the brain astrocytes, macrophages T-cells, and immune system organs as well as the structure and functioning of neurons were more pronounced in the young mice. Conclusion: We have observed the involvement of the astrocytes, macrophages, T-cells, neural stem cells, and neurons in the brain reaction of mice different age after administration of neurotoxin cuprizone and melatonin. The brain cell composition reaction has the age features. The neuroprotective effects of melatonin in cuprizone-treated mice have been realized through an improvement of the brain cell composition and oxidative stress factors and functioning of bone marrow and thymus.

Prolonged ketamine exposure induces enhanced excitatory GABAergic synaptic activity in the anterior cingulate cortex of neonatal rats.

Experimental studies have indicated that prolonged ketamine exposure in neonates at anesthetic doses causes neuronal apoptosis, which contributes to long-term impairments of learning and memory later in life. The neuronal excitotoxicity mediated by compensatory upregulation of N-methyl-d-aspartate receptors (NMDARs) is proposed to be the underlying mechanism. However, this view does not convincingly explain why excitotoxicity-related apoptotic injury develops selectively in immature neurons. We proposed that the GABAA receptors (GABAARs)-mediated excitatory synaptic signaling due to high expression of the Na+-K+-2Cl- co-transporter (NKCC1), occurring during the early neuronal development period, plays a distinct role in the susceptibility of immature neurons to ketamine-induced injury. Using whole-cell patch-clamp recordings from the forebrain slices containing the anterior cingulate cortex, we found that in vivo repeated ketamine administration significantly induced neuronal hyperexcitability in neonatal, but not adolescent, rats. Such hyperexcitability was accompanied by the increase both in GABAAR- and NMDAR-mediated synaptic transmissions. An interference with the NKCC1 by bumetanide treatment completely reversed these enhanced effects of ketamine exposure and blocked GABAAR-mediated postsynaptic current activity. Thus, these findings were significant as they showed, for the first time, that GABAAR-mediated excitatory action may contribute distinctly to neuronal excitotoxic effects of ketamine on immature neurons in the developing brain.

Common genetic variation in humans impacts in vitro susceptibility to SARS-CoV-2 infection.

The host response to SARS-CoV-2, the etiologic agent of the COVID-19 pandemic, demonstrates significant inter-individual variability. In addition to showing more disease in males, the elderly, and individuals with underlying comorbidities, SARS-CoV-2 can seemingly render healthy individuals with profound clinical complications. We hypothesize that, in addition to viral load and host antibody repertoire, host genetic variants also impact vulnerability to infection. Here we apply human induced pluripotent stem cell (hiPSC)-based models and CRISPR-engineering to explore the host genetics of SARS-CoV-2. We demonstrate that a single nucleotide polymorphism (rs4702), common in the population at large, and located in the 3'UTR of the protease FURIN, impacts alveolar and neuron infection by SARS-CoV-2 in vitro. Thus, we provide a proof-of-principle finding that common genetic variation can impact viral infection, and thus contribute to clinical heterogeneity in SARS-CoV-2. Ongoing genetic studies will help to better identify high-risk individuals, predict clinical complications, and facilitate the discovery of drugs that might treat disease.

Synergistic effect of copper and arsenic upon oxidative stress, inflammation and autophagy alterations in brain tissues of Gallus gallus.

Arsenic or copper is one of the most highly toxic pollution that can cause dysfunction to brains, however, the exact mechanism remains unclear. The aim of the study is to investigate the mechanisms of arsenic or/and copper-induced oxidative stress, inflammation and autophagy in chicken brains and elucidate the interactions between arsenic and copper. A total of 72 1-day-old Hy-line chickens were divided into four groups (18 chickens per group) treated with 30mg/kg arsenic trioxide (As2O3) or/and 300mg/kg copper sulfate (CuSO4) for 12weeks. Histological signs of inflammation were found in the cerebrum, cerebellum and brainstem exposure to arsenic or/and copper. The malondialdehyde (MDA) content were up-regulation, whereas oxidative damage parameters total antioxidant capacity (T-AOC), glutathione (GSH), the inhibition ability of hydroxyl radical (OH), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly decreased (P<0.05). The mRNA levels and protein expressions of inflammation markers, such as nuclear factor kappa B (NF-κB), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and prostaglandin E synthase (PTGEs) were significantly increased (P<0.05). The mRNA levels and protein expressions of autophagy markers including phosphatidylinositol 3-kinase (PI3K), Akt, autophagy-related gene 5 (ATG5), microtubule-associated protein light chains 3 (LC3), ATG4B, and Becline1 in different regions of brains were up-regulation (P<0.05), except the mammalian target of rapamycin complex (mTORC). In conclusion, we speculated that arsenic or copper could induce oxidative stress, inflammation and autophagy in chicken brains, and there may have a synergistic effect between copper and arsenic.

Methods for Mapping Neuronal Activity to Synaptic Connectivity: Lessons From Larval Zebrafish.

For a mechanistic understanding of neuronal circuits in the brain, a detailed description of information flow is necessary. Thereby it is crucial to link neuron function to the underlying circuit structure. Multiphoton calcium imaging is the standard technique to record the activity of hundreds of neurons simultaneously. Similarly, recent advances in high-throughput electron microscopy techniques allow for the reconstruction of synaptic resolution wiring diagrams. These two methods can be combined to study both function and structure in the same specimen. Due to its small size and optical transparency, the larval zebrafish brain is one of the very few vertebrate systems where both, activity and connectivity of all neurons from entire, anatomically defined brain regions, can be analyzed. Here, we describe different methods and the tools required for combining multiphoton microscopy with dense circuit reconstruction from electron microscopy stacks of entire brain regions in the larval zebrafish.

Effect on Acetylcholinesterase and Anti-oxidant Activity of Synthetic Chalcones having a Good Predicted Pharmacokinetic Profile.

BACKGROUND: Acetylcholinesterase (AChE) is an important target in the development of drug to treat Alzheimer's disease (AD). In this work, we investigated the effect of twenty-two synthesized chalcones on AChE activity. OBJECTIVE: This work is aimed to synthesize and evaluate the effect of chalcones on the AChE activity, as well as anti-oxidant activity and predict their pharmacokinetic profile. METHOD: Chalcones were synthesized through a Claisen-Schmidt condensation and their inhibitory effect on the AChE was evaluated by the Elmann's colorimetric method. To determine the anti-oxidant activity the DPPH radical scavenging method was chosen. RESULTS: We found that all chalcones inhibit this activity, with IC50 values ranging from 0.008 to 4.8 µM. We selected the most active compound 19 with an IC50 value of 0.008 µM for a kinetic study demonstrating a competitive inhibition mode. Molecular docking simulations showed a good interaction between 19 and the active site of AChE. Considering the prediction of pharmacokinetic parameters being a useful tool for selecting potential drug candidates, our study results suggest that the majority of chalcones, including the most active one, have a promising pharmacokinetic profile and blood-brain barrier permeability. The involvement of reactive oxygen species (ROS) in AD-related events has encouraged us to evaluate these chalcones as radical scavengers. CONCLUSION: We have found that compound 19 is a potent AChE inhibitor, and based on kinetic studies, it acts as a competitive inhibitor.