Electroacupuncture promotes the repair of the damaged spinal cord in mice by mediating neurocan-perineuronal net.

AIMS: This study aimed to investigate the effect of perineuronal net (PNN) and neurocan (NCAN) on spinal inhibitory parvalbumin interneuron (PV-IN), and the mechanism of electroacupuncture (EA) in promoting spinal cord injury (SCI) repair through neurocan in PNN. METHODS: A mouse model of SCI was established. Sham-operated mice or SCI model mice were treated with chondroitin sulfate ABC (ChABC) enzyme or control vehicle for 2 weeks (i.e., sham+veh group, sham+ChABC group, SCI+veh group, and SCI+ChABC group, respectively), and then spinal cord tissues were taken from the T10 lesion epicenter for RNA sequencing (RNA-seq). MSigDB Hallmark and C5 databases for functional analysis, analysis strategies such as differential expression gene analysis (DEG), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA), and protein-protein interaction (PPI). According to the results of RNA-seq analysis, the expression of NCAN was knocked down or overexpressed by virus intervention, or/and EA intervention. Polymerase chain reaction (PCR), immunofluorescence, western blot, electrophysiological, and behavioral tests were performed. RESULTS: After the successful establishment of SCI model, the motor dysfunction of lower limbs, and the expression of PNN core glycan protein at the epicenter of SCI were reduced. RNA-seq and PCR showed that PNN core proteoglycans except NCAN showed the same expression trend in normal and injured spinal cord treated with ChABC. KEGG and GSEA showed that PNN is mainly associated with inhibitory GABA neuronal function in injured spinal cord tissue, and PPI showed that NCAN in PNN can be associated with inhibitory neuronal function through parvalbumin (PV). Calcium imaging showed that local parvalbumin interneuron (PV-IN) activity decreased after PNN destruction, whether due to ChABC treatment or surgical bruising of the spinal cord. Overexpression of neurocan in injured spinal cord can enhance local PV-IN activity. PCR and western blot suggested that overexpression or knockdown of neurocan could up-regulate or down-regulate the expression of GAD. At the same time, the activity of PV-IN in the primary motor cortex (M1) and the primary sensory cortex of lower (S1HL) extremity changed synchronously. In addition, overexpression of neurocan improved the electrical activity of the lower limb and promoted functional repair of the paralyzed hind limb. EA intervention reversed the down-regulation of neurocan, enhanced the expression of PNN in the lesioned area, M1 and S1HL. CONCLUSION: Neurocan in PNN can regulate the activity of PV-IN, and EA can promote functional recovery of mice with SCI by upregulating neurocan expression in PNN.

Azadiradione up-regulates the expression of parvalbumin and BDNF via Ube3a.

Azadiradione is a small bioactive limonoid found in the seed of Azadirachta Indica, an Indian medicinal plant commonly known as Neem. Recently, it has been shown to ameliorate the disease pathology in fly and mouse model of Huntington's disease by restoring impaired proteostasis. Here we report that the azadiradione could be involved in modulating the synaptic function through increased expression of Ube3a, a dual function protein having ubiquitin ligase and co-activator functions and associated with Angelman syndrome and autism. Treatment of azadiradione to HT22 hippocampal cell line and in adult mice induced the expression of Ube3a as well as two important synaptic function and plasticity regulating proteins, parvalbumin and brain-derived neurotropic factor (BDNF). Interestingly, another synaptic plasticity modulating protein Arc (activity-regulated cytoskeletal associated protein) was down-regulated by azadiradione. Partial knockdown of Ube3a in HT22 cell abrogated azadiradione induced expression of parvalbumin and BDNF. Ube3a-maternal deficient mice also exhibited significantly decreased expression of parvalbumin and BDNF in their brain and treatment of azadiradione in these animals did not rescue the altered expression of either parvalbumin or BDNF. These results indicate that azadiradione-induced expression of parvalbumin and BDNF in the brain is mediated through Ube3a and suggest that azadiradione could be implicated in restoring synaptic dysfunction in many neuropsychiatric/neurodegenerative disorders.

Circuit mechanism for suppression of frontal cortical ignition during NREM sleep.

Conscious perception is greatly diminished during sleep, but the underlying circuit mechanism is poorly understood. We show that cortical ignition-a brain process shown to be associated with conscious awareness in humans and non-human primates-is strongly suppressed during non-rapid-eye-movement (NREM) sleep in mice due to reduced cholinergic modulation and rapid inhibition of cortical responses. Brain-wide functional ultrasound imaging and cell-type-specific calcium imaging combined with optogenetics showed that activity propagation from visual to frontal cortex is markedly reduced during NREM sleep due to strong inhibition of frontal pyramidal neurons. Chemogenetic activation and inactivation of basal forebrain cholinergic neurons powerfully increased and decreased visual-to-frontal activity propagation, respectively. Furthermore, although multiple subtypes of dendrite-targeting GABAergic interneurons in the frontal cortex are more active during wakefulness, soma-targeting parvalbumin-expressing interneurons are more active during sleep. Chemogenetic manipulation of parvalbumin interneurons showed that sleep/wake-dependent cortical ignition is strongly modulated by perisomatic inhibition of pyramidal neurons.

Comparative features of calretinin, calbindin, and parvalbumin expressing interneurons in mouse and monkey primary visual and frontal cortices.

Fundamental differences in excitatory pyramidal cells across cortical areas and species highlight the implausibility of extrapolation from mouse to primate neurons and cortical networks. Far less is known about comparative regional and species-specific features of neurochemically distinct cortical inhibitory interneurons. Here, we quantified the density, laminar distribution, and somatodendritic morphology of inhibitory interneurons expressing one or more of the calcium-binding proteins (CaBPs) (calretinin [CR], calbindin [CB], and/or parvalbumin [PV]) in mouse (Mus musculus) versus rhesus monkey (Macaca mulatta) in two functionally and cytoarchitectonically distinct regions-the primary visual and frontal cortical areas-using immunofluorescent multilabeling, stereological counting, and 3D reconstructions. There were significantly higher densities of CB+ and PV+ neurons in visual compared to frontal areas in both species. The main species difference was the significantly greater density and proportion of CR+ interneurons and lower extent of CaBP coexpression in monkey compared to mouse cortices. Cluster analyses revealed that the somatodendritic morphology of layer 2-3 inhibitory interneurons is more dependent on CaBP expression than on species and area. Only modest effects of species were observed for CB+ and PV+ interneuron morphologies, while CR+ neurons showed no difference. By contrast to pyramidal cells that show highly distinctive area- and species-specific features, here we found more subtle differences in the distribution and features of interneurons across areas and species. These data yield insight into how nuanced differences in the population organization and properties of neurons may underlie specializations in cortical regions to confer species- and area-specific functional capacities.

Possible Involvement of Perineuronal Nets in Anti-Depressant Effects of Electroacupuncture in Chronic-Stress-Induced Depression in Rats.

Acupuncture can alleviate depression-like behaviors. However, the neural mechanisms behind the anti-depressive effect remain unknown. Perineuronal net (PNN) abnormalities have been reported in multiple psychiatric disorders. This study investigated the modulation and neural mechanism of PNNs in the anti-depressant process of electroacupuncture (EA) at Baihui (GV20) and Yintang (GV29) points. A rat depression model was induced by chronic unpredicted mild stress (CUMS). The results revealed that CUMS, applied for four weeks, specifically reduces PNNs around parvalbumin (PV). In addition, EA and fluoxetine treatments reverse the decrease in PNNs+ cell density and the ratio of PV and PNN double-positive cells to PV+ neurons in the medial prefrontal cortex (mPFC) after CUMS. Furthermore, EA treatment can reverse the decrease in the protein expression of PNN components (aggrecan and brevican) in the mPFC caused by stress. After EA treatment, the decreased expression of GAD67, GLuA1, and PSD95 in the mPFC induced by CUMS for four weeks was also reversed. PNN degradation in mPFC brain areas potentially interferes with the anti-depressant benefits of EA in rats with depression induced by CUMS. EA treatment did not increase PNNs+ cell density and the ratio of PV and PNN double-positive cells to PV+ neurons after PNNs degradation in the mPFC brain region of rats. This finding indicated that the mechanism of acupuncture's anti-depressant effect may be based on reversing the CUMS-induced decline in PNN expression, the functional impairment of γ-aminobutyric acid (GABA) neurons, and the regulation of excitatory synaptic proteins expression.

A thalamic-primary auditory cortex circuit mediates resilience to stress.

Resilience enables mental elasticity in individuals when rebounding from adversity. In this study, we identified a microcircuit and relevant molecular adaptations that play a role in natural resilience. We found that activation of parvalbumin (PV) interneurons in the primary auditory cortex (A1) by thalamic inputs from the ipsilateral medial geniculate body (MG) is essential for resilience in mice exposed to chronic social defeat stress. Early attacks during chronic social defeat stress induced short-term hyperpolarizations of MG neurons projecting to the A1 (MGA1 neurons) in resilient mice. In addition, this temporal neural plasticity of MGA1 neurons initiated synaptogenesis onto thalamic PV neurons via presynaptic BDNF-TrkB signaling in subsequent stress responses. Moreover, optogenetic mimicking of the short-term hyperpolarization of MGA1 neurons, rather than merely activating MGA1 neurons, elicited innate resilience mechanisms in response to stress and achieved sustained antidepressant-like effects in multiple animal models, representing a new strategy for targeted neuromodulation.

Organization of Cortical and Thalamic Input to Inhibitory Neurons in Mouse Motor Cortex.

Intracortical inhibition in motor cortex (M1) regulates movement and motor learning. If cortical and thalamic inputs target different inhibitory cell types in different layers, then these afferents may play different roles in regulating M1 output. Using mice of both sexes, we quantified input to two main classes of M1 interneurons, parvalbumin+ (PV+) cells and somatostatin+ (SOM+) cells, using monosynaptic rabies tracing. We then compared anatomic and functional connectivity based on synaptic strength from sensory cortex and thalamus. Functionally, each input innervated M1 interneurons with a unique laminar profile. Different interneuron types were excited in a distinct, complementary manner, suggesting feedforward inhibition proceeds selectively via distinct circuits. Specifically, somatosensory cortex (S1) inputs primarily targeted PV+ neurons in upper layers (L2/3) but SOM+ neurons in middle layers (L5). Somatosensory thalamus [posterior nucleus (PO)] inputs targeted PV+ neurons in middle layers (L5). In contrast to sensory cortical areas, thalamic input to SOM+ neurons was equivalent to that of PV+ neurons. Thus, long-range excitatory inputs target inhibitory neurons in an area and a cell type-specific manner, which contrasts with input to neighboring pyramidal cells. In contrast to feedforward inhibition providing generic inhibitory tone in cortex, circuits are selectively organized to recruit inhibition matched to incoming excitatory circuits.SIGNIFICANCE STATEMENT M1 integrates sensory information and frontal cortical inputs to plan and control movements. Although inputs to excitatory cells are described, the synaptic circuits by which these inputs drive specific types of M1 interneurons are unknown. Anatomical results with rabies tracing and physiological quantification of synaptic strength shows that two main classes of inhibitory cells (PV+ and SOM+ interneurons) both receive substantial cortical and thalamic input, in contrast to interneurons in sensory areas (where thalamic input strongly prefers PV+ interneurons). Further, each input studied targets PV+ and SOM+ interneurons in a different fashion, suggesting that separate, specific circuits exist for recruitment of feedforward inhibition.

Calcium Activation of Parvalbumin Neurons Induced by Electrical Motor Cortex Stimulation.

Electrical motor cortex stimulation (EMCS) has been used for Parkinson's Disease (PD) treatment. Some studies found that distinct cell types might lead to selective effects. As the largest subgroup of interneurons, Parvalbumin (PV) neurons have been reported to be involved in the mechanisms of therapeutic efficacy for PD treatment. However, little is known about their responses to the EMCS. In this study, we used in-vivo two-photon imaging to record calcium activities of PV neurons (specific type) and all neurons (non-specific type) in layer 2/3 primary motor cortex (MI) during EMCS with various stimulus parameters. We found PV neurons displayed different profiles of activation property compared to all neurons. The cathodal polarity preference of PV neurons decreased at a high-frequency stimulus. The calcium transients of PV neurons generated by EMCS trended to be with large amplitude and short active duration. The optimal activation frequency of PV neurons is higher than that of all neurons. These results improved our understanding of the selective effects of EMCS on specific cell types, which could bring more effective stimulation protocols for PD treatment.

"Ependymal-in" Gradient of Thalamic Damage in Progressive Multiple Sclerosis.

Leptomeningeal and perivenular infiltrates are important contributors to cortical grey matter damage and disease progression in multiple sclerosis (MS). Whereas perivenular inflammation induces vasculocentric lesions, leptomeningeal involvement follows a subpial "surface-in" gradient. To determine whether similar gradient of damage occurs in deep grey matter nuclei, we examined the dorsomedial thalamic nuclei and cerebrospinal fluid (CSF) samples from 41 postmortem secondary progressive MS cases compared with 5 non-neurological controls and 12 controls with other neurological diseases. CSF/ependyma-oriented gradient of reduction in NeuN+ neuron density was present in MS thalamic lesions compared to controls, greatest (26%) in subventricular locations at the ependyma/CSF boundary and least with increasing distance (12% at 10 mm). Concomitant graded reduction in SMI31+ axon density was observed, greatest (38%) at 2 mm from the ependyma/CSF boundary and least at 10 mm (13%). Conversely, gradient of major histocompatibility complex (MHC)-II+ microglia density increased by over 50% at 2 mm at the ependyma/CSF boundary and only by 15% at 10 mm and this gradient inversely correlated with the neuronal (R = -0.91, p < 0.0001) and axonal (R = -0.79, p < 0.0001) thalamic changes. Observed gradients were also detected in normal-appearing thalamus and were associated with rapid/severe disease progression; presence of leptomeningeal tertiary lymphoid-like structures; large subependymal infiltrates, enriched in CD20+ B cells and occasionally containing CXCL13+ CD35+ follicular dendritic cells; and high CSF protein expression of a complex pattern of soluble inflammatory/neurodegeneration factors, including chitinase-3-like-1, TNFR1, parvalbumin, neurofilament-light-chains and TNF. Substantial "ependymal-in" gradient of pathological cell alterations, accompanied by presence of intrathecal inflammation, compartmentalized either in subependymal lymphoid perivascular infiltrates or in CSF, may play a key role in MS progression. SUMMARY FOR SOCIAL MEDIA: Imaging and neuropathological evidences demonstrated the unique feature of "surface-in" gradient of damage in multiple sclerosis (MS) since early pediatric stages, often associated with more severe brain atrophy and disease progression. In particular, increased inflammation in the cerebral meninges has been shown to be strictly associated with an MS-specific gradient of neuronal, astrocyte, and oligodendrocyte loss accompanied by microglial activation in subpial cortical layers, which is not directly related to demyelination. To determine whether a similar gradient of damage occurs in deep grey matter nuclei, we examined the potential neuronal and microglia alterations in the dorsomedial thalamic nuclei from postmortem secondary progressive MS cases in combination with detailed neuropathological characterization of the inflammatory features and protein profiling of paired CSF samples. We observed a substantial "subependymal-in" gradient of neuro-axonal loss and microglia activation in active thalamic lesions of progressive MS cases, in particular in the presence of increased leptomeningeal and cerebrospinal fluid (CSF) inflammation. This altered graded pathology was found associated with more severe and rapid progressive MS and increased inflammatory degree either in large perivascular subependymal infiltrates, enriched in B cells, or within the paired CSF, in particular with elevated levels of a complex pattern of soluble inflammatory and neurodegeneration factors, including chitinase 3-like-1, TNFR1, parvalbumin, neurofilament light-chains and TNF. These data support a key role for chronic, intrathecally compartmentalized inflammation in specific disease endophenotypes. CSF biomarkers, together with advance imaging tools, may therefore help to improve not only the disease diagnosis but also the early identification of specific MS subgroups that would benefit of more personalized treatments. ANN NEUROL 2022;92:670-685.

Neurogenesis and neuronal differentiation in the postnatal frontal cortex in Down syndrome.

Although Down syndrome (DS), the most common developmental genetic cause of intellectual disability, displays proliferation and migration deficits in the prenatal frontal cortex (FC), a knowledge gap exists on the effects of trisomy 21 upon postnatal cortical development. Here, we examined cortical neurogenesis and differentiation in the FC supragranular (SG, II/III) and infragranular (IG, V/VI) layers applying antibodies to doublecortin (DCX), non-phosphorylated heavy-molecular neurofilament protein (NHF, SMI-32), calbindin D-28K (Calb), calretinin (Calr), and parvalbumin (Parv), as well as ß-amyloid (APP/Aß and Aß1-42) and phospho-tau (CP13 and PHF-1) in autopsy tissue from age-matched DS and neurotypical (NTD) subjects ranging from 28-weeks (wk)-gestation to 3 years of age. Thionin, which stains Nissl substance, revealed disorganized cortical cellular lamination including a delayed appearance of pyramidal cells until 44 wk of age in DS compared to 28 wk in NTD. SG and IG DCX-immunoreactive (-ir) cells were only visualized in the youngest cases until 83 wk in NTD and 57 wk DS. Strong SMI-32 immunoreactivity was observed in layers III and V pyramidal cells in the oldest NTD and DS cases with few appearing as early as 28 wk of age in layer V in NTD. Small Calb-ir interneurons were seen in younger NTD and DS cases compared to Calb-ir pyramidal cells in older subjects. Overall, a greater number of Calb-ir cells were detected in NTD, however, the number of Calr-ir cells were comparable between groups. Diffuse APP/Aß immunoreactivity was found at all ages in both groups. Few young cases from both groups presented non-neuronal granular CP13 immunoreactivity in layer I. Stronger correlations between brain weight, age, thionin, DCX, and SMI-32 counts were found in NTD. These findings suggest that trisomy 21 affects postnatal FC lamination, neuronal migration/neurogenesis and differentiation of projection neurons and interneurons that likely contribute to cognitive impairment in DS.

Paradoxical somatodendritic decoupling supports cortical plasticity during REM sleep.

Rapid eye movement (REM) sleep is associated with the consolidation of emotional memories. Yet, the underlying neocortical circuits and synaptic mechanisms remain unclear. We found that REM sleep is associated with a somatodendritic decoupling in pyramidal neurons of the prefrontal cortex. This decoupling reflects a shift of inhibitory balance between parvalbumin neuron-mediated somatic inhibition and vasoactive intestinal peptide-mediated dendritic disinhibition, mostly driven by neurons from the central medial thalamus. REM-specific optogenetic suppression of dendritic activity led to a loss of danger-versus-safety discrimination during associative learning and a lack of synaptic plasticity, whereas optogenetic release of somatic inhibition resulted in enhanced discrimination and synaptic potentiation. Somatodendritic decoupling during REM sleep promotes opposite synaptic plasticity mechanisms that optimize emotional responses to future behavioral stressors.

Possible Role of Parvalbumin Interneurons in Meditation and Psychiatric Illness.

Parvalbumin (PV) interneurons are present in multiple brain regions and produce complex influences on brain functioning. An increasing number of research findings indicate that the function of these interneurons is more complex than solely to inhibit pyramidal neurons in the cortex. They generate feedback and feedforward inhibition of cortical neurons, and they are critically involved in the generation of neuronal network oscillation. These oscillations, generated by various brain regions, are linked to perceptions, thought processes, and cognitive functions, all of which, in turn, influence human emotions and behavior. Both animal and human studies consistently have found that meditation practice results in enhancement in the effects of alpha-, theta-, and gamma-frequency oscillations, which may correspond to positive changes in cognition, emotion, conscious awareness, and, subsequently, behavior. Although the study of meditation has moved into mainstream neuroscience research, the link between PV interneurons and any role they might play in meditative states remains elusive. This article is focused primarily on gamma-frequency oscillation, which is generated by PV interneurons, to develop insight and perspective into the role of PV interneurons in meditation. This article also points to new and emerging directions that address whether this role of PV interneurons in meditation extends to a beneficial, and potentially therapeutic, role in the treatment of common psychiatric disorders, including schizophrenia.

A Novel Layer 4 Corticofugal Cell Type/Projection Involved in Thalamo-Cortico-Striatal Sensory Processing.

In sensory cortices, the information flow has been thought to be processed vertically across cortical layers, with layer 4 being the major thalamo-recipient which relays thalamic signals to layer 2/3, which in turn transmits thalamic information to layer 5 and 6 to then leave the cortex to reach subcortical and cortical long-range structures. Although several exceptions to this model have been described, neurons in layer 4 are still considered to establish only local (i.e., interlaminar and short-range) connections. Here, taking advantage of anatomic, electrophysiological, and optogenetic techniques, we describe, for the first time, a long-range corticostriatal class of pyramidal neurons in layer 4 (CS-L4) of the mouse auditory cortex that receive direct thalamic inputs. The CS-L4 neurons are embedded in a feedforward inhibitory circuit involving local parvalbumin neurons and establish connections in the posterior striatum in yet another feedforward inhibitory thalamo→cortico(L4)→striatal circuit which potentially contributes in controlling control the output of striatal spiny projection neurons.SIGNIFICANCE STATEMENT The assumption has been that layer 4 neurons are the main thalamic recipient layer, projecting to the upper cortical layer 2/3. However, no study has revealed a detailed understanding of the circuit mechanisms by which layer 4 sends a projection to a subcortical structure, such as the striatum, and differentially innervate the spiny projection neurons (SPNs) and intrastriatal parvalbumin-expressing neurons. For the first time, our results demonstrate that the auditory cortex projects to the posterior part of the dorsal striatum via pyramidal neurons located in layer 4 (CS-L4 neurons). Here we propose a new wiring diagram that implemented the old one, in which layer 4 is not only involved in the transfer of thalamic input to the upper layer 2/3, but can also exert a direct top-down control, bypassing intracortical processing of subcortical structures, such as the posterior part of the dorsal striatum. This poses a new conceptual cell element (CS-L4 neurons) for experimental and theoretical work of the cortical function.

Hippocampal and thalamic afferents form distinct synaptic microcircuits in the mouse infralimbic frontal cortex.

The selection of goal-directed behaviors is supported by neural circuits located within the frontal cortex. Frontal cortical afferents arise from multiple brain areas, yet the cell-type-specific targeting of these inputs is unclear. Here, we use monosynaptic retrograde rabies mapping to examine the distribution of afferent neurons targeting distinct classes of local inhibitory interneurons and excitatory projection neurons in mouse infralimbic frontal cortex. Interneurons expressing parvalbumin, somatostatin, or vasoactive intestinal peptide receive a large proportion of inputs from the hippocampus, while interneurons expressing neuron-derived neurotrophic factor receive a large proportion of inputs from thalamic regions. A similar dichotomy is present among the four different excitatory projection neurons. These results show a prominent bias among long-range hippocampal and thalamic afferent systems in their targeting to specific sets of frontal cortical neurons. Moreover, they suggest the presence of two distinct local microcircuits that control how different inputs govern frontal cortical information processing.

Hippocampal and Reticulo-Thalamic Parvalbumin Interneurons and Synaptic Re-Organization during Sleep Disorders in the Rat Models of Parkinson's Disease Neuropathology.

We investigated the alterations of hippocampal and reticulo-thalamic (RT) GABAergic parvalbumin (PV) interneurons and their synaptic re-organizations underlying the prodromal local sleep disorders in the distinct rat models of Parkinson's disease (PD). We demonstrated for the first time that REM sleep is a predisposing state for the high-voltage sleep spindles (HVS) induction in all experimental models of PD, particularly during hippocampal REM sleep in the hemiparkinsonian models. There were the opposite underlying alterations of the hippocampal and RT GABAergic PV+ interneurons along with the distinct MAP2 and PSD-95 expressions. Whereas the PD cholinopathy enhanced the number of PV+ interneurons and suppressed the MAP2/PSD-95 expression, the hemiparkinsonism with PD cholinopathy reduced the number of PV+ interneurons and enhanced the MAP2/PSD-95 expression in the hippocampus. Whereas the PD cholinopathy did not alter PV+ interneurons but partially enhanced MAP2 and suppressed PSD-95 expression remotely in the RT, the hemiparkinsonism with PD cholinopathy reduced the PV+ interneurons, enhanced MAP2, and did not change PSD-95 expression remotely in the RT. Our study demonstrates for the first time an important regulatory role of the hippocampal and RT GABAergic PV+ interneurons and the synaptic protein dynamic alterations in the distinct rat models of PD neuropathology.

Timely N-Acetyl-Cysteine and Environmental Enrichment Rescue Oxidative Stress-Induced Parvalbumin Interneuron Impairments via MMP9/RAGE Pathway: A Translational Approach for Early Intervention in Psychosis.

Research in schizophrenia (SZ) emphasizes the need for new therapeutic approaches based on antioxidant/anti-inflammatory compounds and psycho-social therapy. A hallmark of SZ is a dysfunction of parvalbumin-expressing fast-spiking interneurons (PVI), which are essential for neuronal synchrony during sensory/cognitive processing. Oxidative stress and inflammation during early brain development, as observed in SZ, affect PVI maturation. We compared the efficacy of N-acetyl-cysteine (NAC) and/or environmental enrichment (EE) provided during juvenile and/or adolescent periods in rescuing PVI impairments induced by an additional oxidative insult during childhood in a transgenic mouse model with gluthation deficit (Gclm KO), relevant for SZ. We tested whether this rescue was promoted by the inhibition of MMP9/RAGE mechanism, both in the mouse model and in early psychosis (EP) patients, enrolled in a double-blind, randomized, placebo-controlled clinical trial of NAC supplementation for 6 months. We show that a sequential combination of NAC+EE applied after an early-life oxidative insult recovers integrity and function of PVI network in adult Gclm KO, via the inhibition of MMP9/RAGE. Six-month NAC treatment in EP patients reduces plasma sRAGE in association with increased prefrontal GABA, improvement of cognition and clinical symptoms, suggesting similar neuroprotective mechanisms. The sequential combination of NAC+EE reverses long-lasting effects of an early oxidative insult on PVI/perineuronal net (PNN) through the inhibition of MMP9/RAGE mechanism. In analogy, patients vulnerable to early-life insults could benefit from a combined pharmacological and psycho-social therapy.

Generation of mature and functional hair cells by co-expression of Gfi1, Pou4f3, and Atoh1 in the postnatal mouse cochlea.

The mammalian cochlea cannot regenerate functional hair cells (HCs) spontaneously. Atoh1 overexpression as well as other strategies are unable to generate functional HCs. Here, we simultaneously upregulated the expression of Gfi1, Pou4f3, and Atoh1 in postnatal cochlear supporting cells (SCs) in vivo, which efficiently converted SCs into HCs. The newly regenerated HCs expressed HC markers Myo7a, Calbindin, Parvalbumin, and Ctbp2 and were innervated by neurites. Importantly, many new HCs expressed the mature and terminal marker Prestin or vesicular glutamate transporter 3 (vGlut3), depending on the subtypes of the source SCs. Finally, our patch-clamp analysis showed that the new HCs in the medial region acquired a large K+ current, fired spikes transiently, and exhibited signature refinement of ribbon synapse functions, in close resemblance to native wild-type inner HCs. We demonstrated that co-upregulating Gfi1, Pou4f3, and Atoh1 enhances the efficiency of HC generation and promotes the functional maturation of new HCs.

Effect of Berberine Isolated from Barberry Species by Centrifugal Partition Chromatography on Memory and the Expression of Parvalbumin in the Mouse Hippocampus Proper.

Neurodegenerative diseases associated with memory disturbances are important health issues occurring due to a prolonged life span. This article presents the results of a study targeting the emergence of a drug candidate with antiamnesic properties. The effect of berberine (BBR), an isoquinoline alkaloid isolated from the overground parts of Berberis sibirica Pall., on memory and expression of parvalbumin in the mouse hippocampus proper were determined. High-purity BBR was isolated by centrifugal partition chromatography from a methanolic extract from B. sibirica by using a methyl-tert-butyl ether and water (1:1 v/v) solvent system with 10 mmol/L of triethylamine and hydrochloric acid. In an in vivo study, we assessed the influence of the chronic administration of BBR on different stages of memory-related responses in mice. Our results indicated that the chronic administration of BBR in a higher dose (5 mg/kg) improves long-term memory acquisition in mice, as determined in the passive avoidance test. The hippocampal CA1-CA3 fields showed an increased number of parvalbumin-immunoreactive neurons (PV-IR) and nerve fibers as compared to the control. No significant changes in the dentate gyrus were observed between the groups. The HPLC-ESI-QTOF-MS/MS analysis of the biological material revealed the content of BBR as 363.4 ± 15.0 ng (4.11% of RSD) per brain, 15.06 ± 0.89 ng (5.91% of RSD) per hippocampus, and 54.45 ± 1.40 (4.05% of RSD) ng in 100 µL plasma. The study showed that BBR could be a factor influencing the expression of PV in hippocampal neurons. We speculate that BBR may modulate the level of Ca2+ in neurons and thus potentially act as a neuroprotective factor against neuronal damages.

Neonatal valproic acid exposure produces altered gyrification related to increased parvalbumin-immunopositive neuron density with thickened sulcal floors.

Valproic acid (VPA) treatment is associated with autism spectrum disorder in humans, and ferrets can be used as a model to test this; so far, it is not known whether ferrets react to developmental VPA exposure with gyrencephalic abnormalities. The current study characterized gyrification abnormalities in ferrets following VPA exposure during neonatal periods, corresponding to the late stage of cortical neurogenesis as well as the early stage of sulcogyrogenesis. Ferret pups received intraperitoneal VPA injections (200 µg/g of body weight) on postnatal days (PD) 6 and 7. BrdU was administered simultaneously at the last VPA injection. Ex vivo MRI-based morphometry demonstrated significantly lower gyrification index (GI) throughout the cortex in VPA-treated ferrets (1.265 ± 0.027) than in control ferrets (1.327 ± 0.018) on PD 20, when primary sulcogyrogenesis is complete. VPA-treated ferrets showed significantly smaller sulcal-GIs in the rostral suprasylvian sulcus and splenial sulcus but a larger lateral sulcus surface area than control ferrets. The floor cortex of the inner stratum of both the rostral suprasylvian and splenial sulci and the outer stratum of the lateral sulcus showed a relatively prominent expansion. Parvalbumin-positive neuron density was significantly greater in the expanded cortical strata of sulcal floors in VPA-treated ferrets, regardless of the BrdU-labeled status. Thus, VPA exposure during the late stage of cortical neurogenesis may alter gyrification, primarily in the frontal and parietotemporal cortical divisions. Altered gyrification may thicken the outer or inner stratum of the cerebral cortex by increasing parvalbumin-positive neuron density.

Diversity of Receptive Fields and Sideband Inhibition with Complex Thalamocortical and Intracortical Origin in L2/3 of Mouse Primary Auditory Cortex.

Receptive fields of primary auditory cortex (A1) neurons show excitatory neuronal frequency preference and diverse inhibitory sidebands. While the frequency preferences of excitatory neurons in local A1 areas can be heterogeneous, those of inhibitory neurons are more homogeneous. To date, the diversity and the origin of inhibitory sidebands in local neuronal populations and the relation between local cellular frequency preference and inhibitory sidebands are unknown. To reveal both excitatory and inhibitory subfields, we presented two-tone and pure tone stimuli while imaging excitatory neurons (Thy1) and two types of inhibitory neurons (parvalbumin and somatostatin) in L2/3 of mice A1. We classified neurons into six classes based on frequency response area (FRA) shapes and sideband inhibition depended both on FRA shapes and cell types. Sideband inhibition showed higher local heterogeneity than frequency tuning, suggesting that sideband inhibition originates from diverse sources of local and distant neurons. Two-tone interactions depended on neuron subclasses with excitatory neurons showing the most nonlinearity. Onset and offset neurons showed dissimilar spectral integration, suggesting differing circuits processing sound onset and offset. These results suggest that excitatory neurons integrate complex and nonuniform inhibitory input. Thalamocortical terminals also exhibited sideband inhibition, but with different properties from those of cortical neurons. Thus, some components of sideband inhibition are inherited from thalamocortical inputs and are further modified by converging intracortical circuits. The combined heterogeneity of frequency tuning and diverse sideband inhibition facilitates complex spectral shape encoding and allows for rapid and extensive plasticity.SIGNIFICANCE STATEMENT Sensory systems recognize and differentiate between different stimuli through selectivity for different features. Sideband inhibition serves as an important mechanism to sharpen stimulus selectivity, but its cortical mechanisms are not entirely resolved. We imaged pyramidal neurons and two common classes of interneurons suggested to mediate sideband inhibition (parvalbumin and somatostatin positive) in the auditory cortex and inferred their inhibitory sidebands. We observed a higher degree of variability in the inhibitory sideband than in the local frequency tuning, which cannot be predicted from the relative high homogeneity of responses by inhibitory interneurons. This suggests that cortical sideband inhibition is nonuniform and likely results from a complex interplay between existing functional inhibition in the feedforward input and cortical refinement.