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23 pages, 4579 KB  
Article
Chemogenetic Activation of LC Noradrenergic Afferents Facilitates Cerebellar CF–PC LTD via Presynaptic α2A–AR/CDK5/PKA Signaling
by Xu-Dong Zhang, Ying-Han Xu, Wang-Tong Wu, Lang-Yue Zheng, Xin-Yi Xu, Chun-Ping Chu and De-Lai Qiu
Biomolecules 2026, 16(7), 1042; https://doi.org/10.3390/biom16071042 - 17 Jul 2026
Viewed by 261
Abstract
Cerebellar climbing fiber–Purkinje cell (CF–PC) long-term depression (LTD) plays a critical role in motor learning and is modulated by locus coeruleus (LC) noradrenergic afferents via distinct adrenergic receptor (AR) subtypes. Nevertheless, the mechanisms underlying LC noradrenergic neuron-mediated regulation of CF–PC LTD remain poorly [...] Read more.
Cerebellar climbing fiber–Purkinje cell (CF–PC) long-term depression (LTD) plays a critical role in motor learning and is modulated by locus coeruleus (LC) noradrenergic afferents via distinct adrenergic receptor (AR) subtypes. Nevertheless, the mechanisms underlying LC noradrenergic neuron-mediated regulation of CF–PC LTD remain poorly understood. Here, we investigated the effects of chemogenetic activation of LC noradrenergic afferents on CF–PC LTD in cerebellar slices from dopamine β-hydroxylase (DBH)-Cre mice using electrophysiology, glutamate sensor imaging, immunofluorescence and pharmacological approaches. Tetanic stimulation (5 Hz) of CFs induced CF–PC LTD under control conditions, and this LTD was enhanced by chemogenetic activation of LC noradrenergic afferents. Blockade of group I metabotropic glutamate receptors (mGluR1) abolished LTD under control conditions, whereas chemogenetic activation of LC noradrenergic afferents triggered a novel form of CF–PC LTD accompanied by an increased N2/N1 ratio. With mGluR1 blocked, chemogenetic activation of LC noradrenergic afferents failed to trigger the novel CF–PC LTD following blockade of α2-AR or α2A-AR, but not α2B-AR or α2C-AR. Importantly, chemogenetic activation of LC noradrenergic afferents triggered LTD of glutamate fluorescence at CF terminals, which was abolished by blockade of α2-AR or α2A-AR, but not α2B-AR or α2C-AR. Notably, inhibition of either cyclin-dependent kinase 5 (CDK5) or presynaptic, but not postsynaptic, protein kinase A (PKA) completely abolished the CF–PC LTD triggered by chemogenetic activation of LC noradrenergic afferents in mouse cerebellar slices. Immunofluorescence results showed robust α2A-AR expression throughout the cerebellar molecular layer, with intense signals along PC dendrites and clear colocalization with vesicular glutamate transporter 2 (vGluT2) at cerebellar CF terminals. These results indicate that activation of LC noradrenergic afferents potentiates CF–PC LTD by triggering Glu-LTD at CF terminals through the α2A-AR/CDK5/PKA signaling cascade in the mouse cerebellar cortex. Full article
(This article belongs to the Special Issue Regulation of Synapses in the Brain)
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26 pages, 2718 KB  
Review
The Hoffmann Reflex
by Oscar Arias-Carrión and Emmanuel Ortega-Robles
NeuroSci 2026, 7(3), 72; https://doi.org/10.3390/neurosci7030072 - 17 Jun 2026
Viewed by 729
Abstract
The human spinal cord is increasingly recognized as an active and adaptable component of sensorimotor function, contributing to motor control, pain modulation, and recovery after neurological injury. Within this framework, the Hoffmann reflex (H-reflex) has evolved from a classical electrophysiological phenomenon into a [...] Read more.
The human spinal cord is increasingly recognized as an active and adaptable component of sensorimotor function, contributing to motor control, pain modulation, and recovery after neurological injury. Within this framework, the Hoffmann reflex (H-reflex) has evolved from a classical electrophysiological phenomenon into a useful probe of spinal circuit function. Rather than reflecting motoneuron excitability alone, H-reflex amplitude and modulation arise from the interaction of Ia afferent transmission, presynaptic inhibition, homosynaptic depression, and interneuronal networks that regulate sensorimotor gain in a state-dependent manner. This review synthesizes classical and contemporary evidence to position the H-reflex as an indirect measure of spinal inhibitory function in humans. We integrate physiological mechanisms with findings from studies in chronic pain syndromes, spasticity, Parkinson’s disease, and recovery after central nervous system injury, where alterations in spinal inhibitory processes have been described. We further discuss methodological and conceptual challenges that limit clinical translation, including state dependence, protocol heterogeneity, and the lack of normative reference frameworks. Finally, we outline directions for integrating H-reflex paradigms with complementary approaches to improve the interpretation of spinal circuit function and its relation to clinical phenomena. Framed in this context, the H-reflex can be considered a valuable experimental and translational tool, whose utility depends on careful methodological implementation and physiologically informed interpretation. Full article
(This article belongs to the Special Issue New Advances in Neuromodulation Technology)
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23 pages, 3943 KB  
Article
Pregabalin Depresses Cerebellar Parallel Fiber–Purkinje Cell Synaptic Transmission by Modulating Glun2a-Containing Nmda Receptors in Mice In Vitro
by Mei-Rui Li, Xu-Dong Zhang, Li Chen, Yi-Dan Zhang, Chun-Yan Wang, Zi-Yu Zhao, Mo Zhou, Chun-Ping Chu and De-Lai Qiu
Int. J. Mol. Sci. 2026, 27(11), 4660; https://doi.org/10.3390/ijms27114660 - 22 May 2026
Viewed by 387
Abstract
Pregabalin (PGB) exerts its therapeutic effects by binding to the α2δ auxiliary subunits of voltage-gated calcium channels and modulates synaptic transmission in the brain. However, its influence on cerebellar parallel fiber–Purkinje cell (PF–PC) synaptic transmission remains unclear. In the present study, [...] Read more.
Pregabalin (PGB) exerts its therapeutic effects by binding to the α2δ auxiliary subunits of voltage-gated calcium channels and modulates synaptic transmission in the brain. However, its influence on cerebellar parallel fiber–Purkinje cell (PF–PC) synaptic transmission remains unclear. In the present study, we investigated the effects of PGB on PF–PC synaptic transmission using whole-cell patch-clamp recording, glutamate fluorescence imaging, immunohistochemistry, co-immunoprecipitation, Western blotting, and pharmacological approaches. Micro-application of PGB to the cerebellar molecular layer induced a concentration-dependent inhibition of PF–PC excitatory postsynaptic currents (EPSCs), accompanied by an increased paired-pulse ratio. The inhibitory effect of PGB on PF–PC EPSCs was abolished by extracellular blockade of N-methyl-D-aspartate receptors (NMDAR) or their GluN2A subtype, as well as by disruption of α2δ-1–NMDAR complexes, but not by intracellular NMDAR inhibition. Glutamate sensor imaging further showed that PGB markedly reduced the fluorescence intensity of glutamate release evoked by PF stimulation. In the presence of tetrodotoxin (TTX) and a gamma-aminobutyric acid type A (GABAA) receptor antagonist, PGB reduced the frequency of miniature excitatory postsynaptic currents (mEPSCs) without affecting their amplitude. The PGB-induced reduction in mEPSC frequency was fully abolished by extracellular blockade of GluN2A-containing NMDARs or disruption of α2δ-1–NMDAR complexes. Similarly, the inhibitory effects of PGB on PF–PC EPSCs and mEPSCs were eliminated by extracellular PKA inhibition, but not by intracellular protein kinase A (PKA) inhibition. Western blot analysis showed that PGB significantly increased PKA phosphorylation in the molecular layer of the cerebellar cortex. Immunoreactivity for GluN2A and α2δ-1 subunits was colocalized within the molecular layer and abundantly distributed around the dendrites and somata of PCs. Co-immunoprecipitation further verified that α2δ-1 was co-precipitated with GluN1 in cerebellar molecular layer tissue samples. The results indicate that PGB depresses glutamate release from parallel-fiber terminals in the mouse cerebellar cortex through the presynaptic α2δ-1-coupled GluN2A-containing NMDAR/PKA signaling pathway, thereby attenuating PF–PC synaptic transmission. Full article
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16 pages, 885 KB  
Review
Therapeutic Potential Target of Adenosine for Epilepsy: Focusing on Its Interaction with the Molecular Epileptogenic Network
by Xiaoning Zhao, Jiahui Deng, Zhonghua Xiong and Tianfu Li
Biomolecules 2026, 16(3), 453; https://doi.org/10.3390/biom16030453 - 17 Mar 2026
Cited by 2 | Viewed by 979
Abstract
Epilepsy is a neurological disorder characterized by a long-lasting predisposition to recurrently generate unprovoked seizures. Epilepsy affects over 70 million people worldwide, with approximately one-third suffering from pharmacoresistant seizures. Currently, the clinical antiseizure drugs lack efficacy in preventing epileptogenesis. Adenosine, as an endogenous [...] Read more.
Epilepsy is a neurological disorder characterized by a long-lasting predisposition to recurrently generate unprovoked seizures. Epilepsy affects over 70 million people worldwide, with approximately one-third suffering from pharmacoresistant seizures. Currently, the clinical antiseizure drugs lack efficacy in preventing epileptogenesis. Adenosine, as an endogenous anticonvulsant, inhibits the development of epilepsy via interaction with the molecular epileptogenic network on several levels: (i) Activation of A1 receptor inhibits glutamate release via presynaptic inhibition, and hyperpolarizes the synaptic potentials in postsynaptic neurons. (ii) The A2A receptor on astrocytes interacts with astroglial glutamate transporter GLT-1, controlling glial glutamate homeostasis. (iii) Activation of the A3 receptor inhibits GABA transporter type 1-mediated GABA uptake. (iv) Adenosine kinase (ADK) is highlighted as a pathological hallmark of epilepsy, with its distinct isoforms driving different mechanisms. The cytoplasmic short isoform (ADK-S) in astrocytes controls extracellular adenosine and receptor-mediated pathways, whereas the nuclear long isoform (ADK-L) in astrocytes and specific neurons regulates epigenetic mechanisms without relying on adenosine receptors. Collectively, this review clarifies the adenosine system’s critical regulatory role in the epileptogenic network, highlights adenosine receptors and ADK isoforms as promising therapeutic targets for epilepsy, and provides a theoretical basis for developing novel disease-modifying therapies for pharmacoresistant epilepsy while laying a foundation for subsequent preclinical and clinical translation. Full article
(This article belongs to the Special Issue Molecular Biomarkers of Epileptogenesis)
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28 pages, 5437 KB  
Article
Genetic Activation of Locus Coeruleus Noradrenergic Neurons Modulates Cerebellar MF-GrC Synaptic Plasticity via Presynaptic α2-AR/PKA Signaling in Mice
by Ying-Han Xu, Xu-Dong Zhang, Yang Liu, Zhi-Zhi Zhao, Yuan Zheng, De-Lai Qiu and Chun-Ping Chu
Biology 2026, 15(5), 406; https://doi.org/10.3390/biology15050406 - 28 Feb 2026
Cited by 2 | Viewed by 849
Abstract
Locus coeruleus (LC) noradrenergic neurons project their axons to the cerebellar cortex and modulate cerebellar circuit function via distinct adrenergic receptor (AR) subtypes. The present study investigated the mechanism by which optogenetic activation of LC noradrenergic neurons modulates facial stimulation-evoked long-term synaptic plasticity [...] Read more.
Locus coeruleus (LC) noradrenergic neurons project their axons to the cerebellar cortex and modulate cerebellar circuit function via distinct adrenergic receptor (AR) subtypes. The present study investigated the mechanism by which optogenetic activation of LC noradrenergic neurons modulates facial stimulation-evoked long-term synaptic plasticity at cerebellar mossy fiber-granule cell (MF-GrC) synapses in urethane-anesthetized DBH-Cre mice. Blockade of GABAA receptors, 20 Hz facial stimulation induced MF-GrC long-term potentiation (LTP) in the control group, and this LTP was impaired by optogenetic activation of LC noradrenergic neurons via α2-ARs. Meanwhile, facial stimulation induced LTP of glutamate sensor fluorescence in the granular layer, which was abolished by chemogenetic activation of LC noradrenergic neurons. Following NMDA receptor blockade, optogenetic activation of LC noradrenergic neurons triggered facial stimulation-induced MF-GrC long-term depression (LTD) via α2A-ARs. Optogenetically activated LC noradrenergic neuron-induced MF-GrC LTD was abolished by protein kinase A (PKA) inhibition but not by protein kinase C inhibition. Immunofluorescence results revealed abundant α2A-AR expression in the granular layer, with particularly high levels in glomeruli, and no colocalization with the glutamate sensor. These results indicate that optogenetic activation of LC noradrenergic neurons impairs facial stimulation-induced MF-GrC LTP by triggering presynaptic LTD via the α2A-AR/PKA signaling cascade. Full article
(This article belongs to the Section Neuroscience)
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38 pages, 1912 KB  
Review
Glutamate Metabotropic Receptors-Linked Postsynaptic Density Proteins: An Emergent Hub for Antipsychotics’ Regulation of Synaptic Plasticity and Metaplasticity
by Annarita Barone, Licia Vellucci, Anita Nasti, Benedetta Mazza, Federica Iannotta, Felice Iasevoli and Andrea de Bartolomeis
Biomolecules 2026, 16(2), 324; https://doi.org/10.3390/biom16020324 - 19 Feb 2026
Cited by 3 | Viewed by 1530
Abstract
Glutamate metabotropic receptors (mGluRs) and their molecular partners at the postsynaptic density (PSD) represent a highly dynamic molecular hub that integrates multiple neurotransmitter signals and regulates synaptic plasticity and metaplasticity, which are putatively involved in the pathophysiology of psychiatric illnesses, including schizophrenia. Group [...] Read more.
Glutamate metabotropic receptors (mGluRs) and their molecular partners at the postsynaptic density (PSD) represent a highly dynamic molecular hub that integrates multiple neurotransmitter signals and regulates synaptic plasticity and metaplasticity, which are putatively involved in the pathophysiology of psychiatric illnesses, including schizophrenia. Group I mGluRs (mGluR1 and mGluR5) interact with PSD adaptor and scaffolding proteins, such as Homer, Shank, Norbin, and PICK1, as well as intracellular downstream effectors, creating a molecular network that resembles a Lego-like structure, where modular protein interactions fine-tune glutamatergic transmission. Evidence from preclinical research indicates that dysregulation of mGluR expression and function, along with disrupted PSD protein expression, may contribute to the pathophysiology of schizophrenia by altering glutamatergic neurotransmission and synaptic stability. Antipsychotic mechanisms of action may involve, at least in part, the modulation of mGluR activity mediated through PSD proteins. Notably, novel agents that enhance spinogenesis by acting at the level of PSD proteins, such as SPG302, may open promising avenues for therapeutics aimed at restoring synaptic integrity. While Group I mGluRs dominate postsynaptic regulation, Group II (mGluR2/3) and III (mGluR4/6/7/8) receptors -primarily presynaptic- inhibit neurotransmitter release and plasticity, offering complementary therapeutic avenues. Emerging strategies, such as allosteric modulators of mGluRs, aim to rebalance synaptic signaling in treatment-resistant schizophrenia. This review synthesizes how PSD proteins and mGluRs interact in schizophrenia, exploring their potential as druggable targets for novel therapies. Full article
(This article belongs to the Section Molecular Biology)
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13 pages, 2606 KB  
Article
Inhibiting UNC13B Suppresses Cell Proliferation by Upregulating the Apoptotic Pathway in Multiple Myeloma
by Yuan Tao, Lihua Yuan, Yuntian Ding, Rongli Xie, Fangjie Liu, Zhongming Zhang, Xiaojun Xu and Xiaobo Wang
Biomedicines 2025, 13(9), 2086; https://doi.org/10.3390/biomedicines13092086 - 27 Aug 2025
Viewed by 1235
Abstract
Background/Objectives: Multiple myeloma (MM) is the second most common hematological malignancy and remains incurable because of its complex and heterogeneous pathogenesis. UNC13B (unc-13 homolog B) encodes Munc13-2, a presynaptic protein that is involved in vesicle exocytosis. While its role has been explored in [...] Read more.
Background/Objectives: Multiple myeloma (MM) is the second most common hematological malignancy and remains incurable because of its complex and heterogeneous pathogenesis. UNC13B (unc-13 homolog B) encodes Munc13-2, a presynaptic protein that is involved in vesicle exocytosis. While its role has been explored in neurological diseases, its function in cancer biology remains largely uncharacterized. This study aimed to elucidate the role of UNC13B in regulating MM cell proliferation and apoptosis. Methods:UNC13B mRNA expression was assessed across human MM cell lines. ARD cells, which exhibited the highest UNC13B expression, were transduced with a UNC13B-specific shRNA via a lentiviral vector. Cell proliferation, apoptosis, and expression of associated proteins were evaluated by means of the Cell Counting Kit-8 (CCK-8) assay, flow cytometry, and Western blot analysis. Results: UNC13B was significantly upregulated in MM cell lines. The knockdown of UNC13B in ARD cells markedly inhibited cell proliferation and induced apoptosis. These changes were accompanied by the downregulation of proliferation-related proteins and upregulation of pro-apoptotic markers. Western blot analysis suggests that UNC13B may exert its effects by modulating key regulatory proteins, including PINK1, CDK2, AKR7A3, and Bim. Conclusions: Our findings suggest that UNC13B supports MM cell survival and proliferation, potentially through the regulation of oncogenic and apoptotic signaling pathways. UNC13B may represent a novel therapeutic target in multiple myeloma. Full article
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17 pages, 670 KB  
Review
Effect of Botulinum Toxin on Sensori–Motor Integration in Movement Disorders: A Scoping Review
by Animesh Das and Mandar Jog
Toxins 2025, 17(8), 416; https://doi.org/10.3390/toxins17080416 - 16 Aug 2025
Cited by 2 | Viewed by 1975
Abstract
Background: The primary effect of Botulinum toxin (BoNT) is to cause weakness in the injected muscles by inhibiting the release of acetyl choline from presynaptic nerve terminals. Its effect on sensorimotor integration (SMI) has largely been confined to small studies. The aim of [...] Read more.
Background: The primary effect of Botulinum toxin (BoNT) is to cause weakness in the injected muscles by inhibiting the release of acetyl choline from presynaptic nerve terminals. Its effect on sensorimotor integration (SMI) has largely been confined to small studies. The aim of this review is to highlight effect of BoNT on SMI in the context of Parkinson’s disease (PD), Cervical dystonia (CD), and Writer’s cramp (WC). Methods: Using keywords “Botulinum toxin” and “sensorimotor integration” or “Freezing of gait (FOG)” or ‘Tremor”or “Cervical dystonia” or “Parkinson’s disease”, or “Writer’s cramp”, PubMed database was searched for relevant articles supporting our view. The abstracts of all resultant articles (case reports, case series, randomized trials, observational studies) were reviewed to look for evidence of effects of botulinum toxin on SMI. The relevant articles were charted in excel sheet for further full text review. Results: In FOG, chronic BoNT injections may alter central motor patterns with inclusion of alternative striatal systems, cerebellum, and its connections. In tremor, the afferent proprioceptive input may be modified with reduction of intracortical facilitation and increment of intracortical inhibition. In CD, BoNT can restore disorganized cortical somatotrophy, the key pathophysiology behind cervical dystonia. Similarly, in WC, both the deficient sensory system and abnormal reorganization of the sensorimotor cortex may be altered following chronic BoNT injections. Conclusions: There is preliminary evidence that BoNT may modulate SMI in PD, CD, and WC by altering inputs from the muscle spindles in short term and modifying circuits/particular anatomic cerebral cortices in the long term. Properly conducted randomized trials comparing BoNT with placebo or prospective large-scale studies to look for effect on various surrogate markers reflective of changes in SMI should be the next step to confirm these findings. Targeting the system of afferents like spindles and golgi tendon organs in muscles may be a better way of injecting BoNT, with lower amounts of toxin needed and potential for lesser side-effects like weakness and atrophy. However, this needs to be proven in controlled trials. Full article
(This article belongs to the Special Issue Botulinum Toxins: New Uses in the Treatment of Diseases (2nd Edition))
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21 pages, 6401 KB  
Article
The Dissociation of Latrophilin Fragments by Perfluorooctanoic Acid (PFOA) Inhibits LTXN4C-Induced Neurotransmitter Release
by Evelina Petitto, Jennifer K. Blackburn, M. Atiqur Rahman and Yuri A. Ushkaryov
Toxins 2025, 17(7), 359; https://doi.org/10.3390/toxins17070359 - 20 Jul 2025
Cited by 3 | Viewed by 3792
Abstract
α-Latrotoxin stimulates neurotransmitter release by binding to a presynaptic receptor and then forming ion-permeable membrane pores and/or stimulating the receptor, latrophilin-1, or Adhesion G-protein-coupled receptor type L1 (ADGRL1). To avoid pore formation, we use the mutant α-latrotoxin (LTXN4C), which does not [...] Read more.
α-Latrotoxin stimulates neurotransmitter release by binding to a presynaptic receptor and then forming ion-permeable membrane pores and/or stimulating the receptor, latrophilin-1, or Adhesion G-protein-coupled receptor type L1 (ADGRL1). To avoid pore formation, we use the mutant α-latrotoxin (LTXN4C), which does not form pores and only acts through ADGRL1. ADGRL1 is cleaved into an N-terminal fragment (NTF) and a C-terminal fragment (CTF), which behave as independent cell-surface proteins, reassociating upon binding LTXN4C. We investigated the role of the NTF-CTF association in LTXN4C action, using perfluorooctanoic acid (PFOA). We demonstrate that at low concentrations (≤100 μM) PFOA does not adversely affect ADGRL1-expressing neuroblastoma cells or inhibit LTXN4C binding. However, it causes the dissociation of the NTF-CTF complexes, independent redistribution of the fragments on the cell surface, and their separate internalization. PFOA also promotes the dissociation of NTF-CTF complexes induced by LTXN4C binding. When applied to mouse neuromuscular junctions, PFOA inhibits LTXN4C-induced neurotransmitter release in a concentration-dependent manner. Our results indicate that ADGRL1 can mediate LTXN4C signaling only while its fragments remain associated. These findings explain some aspects of receptor-dependent toxin action and contribute to a mechanistic understanding of ADGRL1 functions in neurons. Full article
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17 pages, 2482 KB  
Article
Heterosynaptic Regulation of α2A-Adrenoceptors on Glutamate/GABA Release in the Prefrontal Cortex of Rats
by Yaru Wei, Yuhan Jiao, Xiaoting He, Xiaodong Tao, Baoming Li and Xuehan Zhang
Biomedicines 2025, 13(6), 1322; https://doi.org/10.3390/biomedicines13061322 - 28 May 2025
Cited by 1 | Viewed by 2744
Abstract
Background/Objectives: Norepinephrine (NE) plays a crucial role in modulating cognitive processes via α2A-adrenoceptors (α2A-ARs) within the prefrontal cortex (PFC), an essential brain region responsible for higher cognitive functions. The α2A-ARs are found on both postsynaptic and presynaptic membranes in the PFC. Previous studies [...] Read more.
Background/Objectives: Norepinephrine (NE) plays a crucial role in modulating cognitive processes via α2A-adrenoceptors (α2A-ARs) within the prefrontal cortex (PFC), an essential brain region responsible for higher cognitive functions. The α2A-ARs are found on both postsynaptic and presynaptic membranes in the PFC. Previous studies have shown that presynaptic α2A-ARs, predominantly located at NE terminals, function as autoreceptors that inhibit NE release. However, the expression of α2A-ARs at non-NE terminals, such as glutamate and GABA, remains ambiguous. To clarify the expression patterns and potential roles of α2A-ARs at non-NE terminals, we investigated their presence at the axon terminals of excitatory glutamate neurons and inhibitory GABA neurons in the rat PFC using immunofluorescence double-labeling, whole-cell patch-clamp recordings, and pharmacological approaches. Methods: To clarify the expression patterns and potential roles of α2A-ARs at non-NE terminals, we investigated their presence at the axon terminals of glutamate neurons and GABA neurons in the rat PFC using immunofluorescence double-labeling, whole-cell patch-clamp recordings, and pharmacological approaches. Results: Our findings delineated the distribution of α2A-ARs at the axon terminals of both glutamate and GABA neurons, and the expression of α2A-AR in the pyramidal neurons within the rat PFC as well. Furthermore, we employed the selective α2A-AR agonist guanfacine to assess the functional role of presynaptic α2A-ARs at these non-NE terminals. Following the application of the PKA inhibitor PKI5–24 to block postsynaptic α2A-AR function, guanfacine still significantly decreased the frequency (not the amplitude) of miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs) in layer 5–6 pyramidal neurons. Notably, the frequency reduction induced by guanfacine persisted even after the depletion of presynaptic NE vesicles. Conclusions: These findings offer a comprehensive analysis of presynaptic α2A-AR expression and function in the PFC, revealing for the first time their role as heteroreceptors that modulate the release of glutamate and GABA. Our results provide morphological and electrophysiological insights into a potential mechanism through which α2A-AR stimulation enhances cognitive functions. Full article
(This article belongs to the Special Issue Synaptic Function and Modulation in Health and Disease)
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17 pages, 2085 KB  
Article
Chronic Fluoxetine Treatment Desensitizes Serotoninergic Inhibition of GABAergic Inputs and Intrinsic Excitability of Dorsal Raphe Serotonin Neurons
by Wei Zhang, Ying Jin and Fu-Ming Zhou
Brain Sci. 2025, 15(4), 384; https://doi.org/10.3390/brainsci15040384 - 8 Apr 2025
Cited by 2 | Viewed by 2760
Abstract
Background: Dorsal raphe serotonin (5-hydroxytryptamine, 5-HT) neurons are spontaneously active and release 5-HT that is critical for normal brain function and regulates mood and emotion. Serotonin reuptake inhibitors (SSRIs) increase the synaptic and extracellular 5-HT level and are effective in treating depression. Treatment [...] Read more.
Background: Dorsal raphe serotonin (5-hydroxytryptamine, 5-HT) neurons are spontaneously active and release 5-HT that is critical for normal brain function and regulates mood and emotion. Serotonin reuptake inhibitors (SSRIs) increase the synaptic and extracellular 5-HT level and are effective in treating depression. Treatment of two weeks or longer is often required for SSRIs to produce clinical benefits. The cellular mechanism underlying this delay is not fully understood. Methods and Results: Using whole-cell patch clamp recording in brain slices, here we show that the GABAergic inputs inhibit the spike firing of raphe 5-HT neurons. This GABAergic regulation was reduced by 5-HT; additionally, this 5-HT effect was prevented by the G-protein-activated inwardly rectifying potassium (GirK) channel inhibitor tertiapin-Q, indicating a contribution of 5-HT activation of GirK channels in GABAergic presynaptic axon terminals. Equally important, after 14 days of treatment with fluoxetine, a widely used SSRI type antidepressant, the 5-HT inhibition of GABAergic inputs was downregulated. Furthermore, chronic fluoxetine treatment downregulated the 5-HT activation of the inhibitory GirK current in 5-HT neurons. Conclusions: Taken together, our results suggest that chronic fluoxetine treatment, by blocking 5-HT reuptake and hence increasing the extracellular 5-HT level, can downregulate the function of 5-HT1B receptors on the GABAergic afferent axon terminals synapsing onto 5-HT neurons, allowing extrinsic GABAergic neurons to more effectively influence 5-HT neurons; simultaneously, chronic fluoxetine treatment also downregulated somatic 5-HT autoreceptor-activated GirK channel-mediated hyperpolarization and decrease in input resistance, rendering 5-HT neurons resistant to autoinhibition and leading to increased 5-HT neuron activity. These neuroplastic changes in raphe 5-HT neurons and their GABAergic afferents may contribute to the behavioral effect of SSRIs. Full article
(This article belongs to the Special Issue How to Rewire the Brain—Neuroplasticity)
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13 pages, 1831 KB  
Article
Chloroquine Causes Aging-like Changes in Diaphragm Neuromuscular Junction Morphology in Mice
by Chloe I. Gulbronson, Sepideh Jahanian, Heather M. Gransee, Gary C. Sieck and Carlos B. Mantilla
Cells 2025, 14(6), 390; https://doi.org/10.3390/cells14060390 - 7 Mar 2025
Viewed by 2510
Abstract
Autophagy impairments have been implicated in various aging conditions. Previous studies in cervical motor neurons show an age-dependent increase in the key autophagy proteins LC3 and p62, reflecting autophagy impairment and autophagosome accumulation. Chloroquine is commonly used to inhibit autophagy by preventing autophagosome–lysosome [...] Read more.
Autophagy impairments have been implicated in various aging conditions. Previous studies in cervical motor neurons show an age-dependent increase in the key autophagy proteins LC3 and p62, reflecting autophagy impairment and autophagosome accumulation. Chloroquine is commonly used to inhibit autophagy by preventing autophagosome–lysosome fusion and may thus emulate the effects of aging on the neuromuscular system. Indeed, acute chloroquine administration in old mice decreases maximal transdiaphragmatic pressure generation, consistent with aging effects. We hypothesized that chloroquine alters diaphragm muscle neuromuscular junction (NMJ) morphology and increases denervation. Adult male and female C57BL/6 × 129J mice between 5 and 8 months of age were used to examine diaphragm muscle NMJ morphology and denervation following daily intraperitoneal injections of chloroquine (10 mg/kg/d) or vehicle for 7 days. The motor end-plates and pre-synaptic terminals were fluorescently labeled with α-bungarotoxin and anti-synaptophysin, respectively. Confocal microscopy was used to assess pre- and post-synaptic morphology and denervation. At diaphragm NMJs, chloroquine treatment decreased pre-synaptic volume by 12% compared to the vehicle (p < 0.05), with no change in post-synaptic volume. Chloroquine treatment increased the proportion of partially denervated NMJs by 2.7-fold compared to vehicle treatment (p < 0.05). The morphological changes observed were similar to those previously reported in the diaphragm muscles of 18-month-old mice. These findings highlight the importance of autophagy in the maintenance of the structural properties at adult NMJs in vivo. Full article
(This article belongs to the Special Issue Experimental Systems to Model Aging Processes)
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46 pages, 1183 KB  
Review
Molecular Anatomy of Synaptic and Extrasynaptic Neurotransmission Between Nociceptive Primary Afferents and Spinal Dorsal Horn Neurons
by Miklós Antal
Int. J. Mol. Sci. 2025, 26(5), 2356; https://doi.org/10.3390/ijms26052356 - 6 Mar 2025
Cited by 12 | Viewed by 7475
Abstract
Sensory signals generated by peripheral nociceptors are transmitted by peptidergic and nonpeptidergic nociceptive primary afferents to the superficial spinal dorsal horn, where their central axon terminals establish synaptic contacts with secondary sensory spinal neurons. In the case of suprathreshold activation, the axon terminals [...] Read more.
Sensory signals generated by peripheral nociceptors are transmitted by peptidergic and nonpeptidergic nociceptive primary afferents to the superficial spinal dorsal horn, where their central axon terminals establish synaptic contacts with secondary sensory spinal neurons. In the case of suprathreshold activation, the axon terminals release glutamate into the synaptic cleft and stimulate postsynaptic spinal neurons by activating glutamate receptors located on the postsynaptic membrane. When overexcitation is evoked by peripheral inflammation, neuropathy or pruritogens, peptidergic nociceptive axon terminals may corelease various neuropeptides, neurotrophins and endomorphin, together with glutamate. However, in contrast to glutamate, neuropeptides, neurotrophins and endomorphin are released extrasynaptically. They diffuse from the site of release and modulate the function of spinal neurons via volume transmission, activating specific extrasynaptic receptors. Thus, the released neuropeptides, neurotrophins and endomorphin may evoke excitation, disinhibition or inhibition in various spinal neuronal populations, and together with glutamate, induce overall overexcitation, called central sensitization. In addition, the synaptic and extrasynaptic release of neurotransmitters is subjected to strong retrograde control mediated by various retrogradely acting transmitters, messengers, and their presynaptic receptors. Moreover, the composition of this complex chemical apparatus is heavily dependent on the actual patterns of nociceptive primary afferent activation in the periphery. This review provides an overview of the complexity of this signaling apparatus, how nociceptive primary afferents can activate secondary sensory spinal neurons via synaptic and volume transmission in the superficial spinal dorsal horn, and how these events can be controlled by presynaptic mechanisms. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Pain)
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14 pages, 1820 KB  
Article
DYRK1A Up-Regulation Specifically Impairs a Presynaptic Form of Long-Term Potentiation
by Aude-Marie Lepagnol-Bestel, Simon Haziza, Julia Viard, Paul A. Salin, Arnaud Duchon, Yann Herault and Michel Simonneau
Life 2025, 15(2), 149; https://doi.org/10.3390/life15020149 - 22 Jan 2025
Cited by 2 | Viewed by 2380
Abstract
Chromosome 21 DYRK1A kinase is associated with a variety of neuronal diseases including Down syndrome. However, the functional impact of this kinase at the synapse level remains unclear. We studied a mouse model that incorporated YAC 152F7 (570 kb), encoding six chromosome 21 [...] Read more.
Chromosome 21 DYRK1A kinase is associated with a variety of neuronal diseases including Down syndrome. However, the functional impact of this kinase at the synapse level remains unclear. We studied a mouse model that incorporated YAC 152F7 (570 kb), encoding six chromosome 21 genes including DYRK1A. The 152F7 mice displayed learning difficulties but their N-methyl-D-aspartate (NMDA)-dependent synaptic long-term potentiation is indistinguishable from non-transgenic animals. We have demonstrated that a presynaptic form of NMDA-independent long-term potentiation (LTP) at the hippocampal mossy fiber was impaired in the 152F7 animals. To obtain insights into the molecular mechanisms involved in such synaptic changes, we analyzed the Dyrk1a interactions with chromatin remodelers. We found that the number of DYRK1A-EP300 and DYRK1A-CREBPP increased in 152F7 mice. Moreover, we observed a transcriptional decrease in genes encoding presynaptic proteins involved in glutamate vesicle exocytosis, namely Rims1, Munc13-1, Syn2 and Rab3A.To refine our findings, we used a mouse BAC 189N3 (152 kb) line that only triplicates the gene Dyrk1a. Again, we found that this NMDA-independent form of LTP is impaired in this mouse line. Altogether, our results demonstrate that Dyrk1a up-regulation is sufficient to specifically inhibit the NMDA-independent form of LTP and suggest that this inhibition is linked to chromatin changes that deregulate genes encoding proteins involved in glutamate synaptic release. Full article
(This article belongs to the Section Medical Research)
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Article
Haloperidol-Induced Catalepsy and Its Correlations with Acetylcholinesterase Activity in Different Brain Structures of Mice
by Brenda Rufino da Silva, Joyce Maria Ferreira Alexandre Lima, Marcela Bermudez Echeverry and Carlos Alberto-Silva
Neurol. Int. 2024, 16(6), 1731-1741; https://doi.org/10.3390/neurolint16060125 - 5 Dec 2024
Cited by 4 | Viewed by 3876
Abstract
Background/Objectives: Antipsychotic medicines are used to treat several psychological disorders and some symptoms caused by dementia and schizophrenia. Haloperidol (Hal) is a typical antipsychotic usually used to treat psychosis; however, its use causes motor or extrapyramidal symptoms (EPS) such as catalepsy. Hal blocks [...] Read more.
Background/Objectives: Antipsychotic medicines are used to treat several psychological disorders and some symptoms caused by dementia and schizophrenia. Haloperidol (Hal) is a typical antipsychotic usually used to treat psychosis; however, its use causes motor or extrapyramidal symptoms (EPS) such as catalepsy. Hal blocks the function of presynaptic D2 receptors on cholinergic interneurons, leading to the release of acetylcholine (ACh), which is hydrolyzed by the enzyme acetylcholinesterase (AChE). Methods: This study was designed to investigate the Hal-inhibitory effects on AChE activity in regions representative of the cholinergic system of mice and potential associations between cataleptic effects generated by Hal using therapeutic doses and their inhibitory effects on AChE. Results: The distribution of the AChE activity in the different regions of the brain followed the order striatum > hippocampus > (prefrontal cortex/hypothalamus/ cerebellum) > brainstem > septo-hippocampal system. In ex vivo assays, Hal inhibited AChE activity obtained from homogenate tissue of the striatum, hippocampus, and septo-hippocampal system in a concentration-dependent manner. The inhibitory concentration of 50% of enzyme activity (IC50) indicated that the septo-hippocampal system required a higher concentration of Hal (IC50 = 202.5 µmol·L−1) to inhibit AChE activity compared to the striatum (IC50 = 162.5 µmol·L−1) and hippocampus (IC50 = 145 µmol·L−1). In in vivo assays, male Swiss mice treated with concentrations of Hal higher than 0.1 mg·kg−1 induced cataleptic effects. Positive correlations with Spearman’s correlation were observed only between the lack of cataleptic effect and the decreased AChE activity of the hippocampus in the mice treated with 0.01 mg·kg−1 of Hal but not in the striatum and septo-hippocampal system. Conclusions: Our results suggest that Hal could increase cholinergic effects via AChE inhibition, in addition to its dopamine antagonist effect, as an alternative approach to the treatment of behavioral disturbances associated with dementia. Full article
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