Biology subjects

Zhang, M.-R.

Publications and source records attributed to Zhang, M.-R..

15 recordsLinked to original sources

bioRxiv2026

Native receptor-targeted chemogenetics enables cell-type-specific inhibition of endogenous receptors in freely moving mice

Understanding brain function requires tools that allow precise manipulation of receptor signaling in defined cell types within intact neural circuits. Optogenetics and conventional chemogenetic approaches primarily enable cell-type-specific control of neuronal excitability using engineered receptors or ion channels. However, direct and reversible inhibition of endogenous neurotransmitter receptors in defined cell types has remained technically inaccessible. Here, we introduce native receptor-targeted chemogenetics (NARCH), a chemogenetic strategy that integrates structure-guided receptor engineering with allosteric ligand design to achieve reversible and temporally precise inhibition of endogenous receptor signaling with cell-type specificity in vivo. By applying NARCH to metabotropic glutamate receptor 1 (mGlu1), we demonstrate that mGlu1 signaling in cerebellar Purkinje cells is required for stabilization of motor learning across training sessions in freely moving mice. NARCH thus establishes a receptor-level chemogenetic framework for causal analysis of neural circuits and behavior.

neuroscience↗

bioRxiv2026

Dopamine shapes brain metastate dynamics

Dopamines influence on large-scale network dynamics, especially on the default mode network (DMN), remains uncertain, as fMRI studies have produced mixed results. One likely contributor to these discrepancies is reliance on traditional functional connectivity analyses, which typically derive a single metric (e.g., the Pearson correlation coefficient) from the entire time series and thus fail to capture network dynamics. To address this issue, we combined a dopaminergic challenge (mazindol, a dopamine transporter [DAT] reuptake inhibitor), PET, resting-state fMRI, and hidden Markov modeling (HMM) to characterize time-varying alterations in human large-scale functional networks following acute DAT blockade. We found that mazindol-induced increases in endogenous dopamine altered the balance between the brains functional "metastates," two recurrent higher-order network configurations that each encompass multiple HMM-derived brain states. Mazindol increased the time participants spent in an internally oriented cognitive metastate and decreased the time spent in a sensorimotor-perceptual metastate, with the DMN showing the most pronounced lengthening. In exploratory analyses, declines in [{superscript 1}{superscript 1}C]raclopride binding, a PET index of D2 dopamine receptor availability reflecting increased striatal extracellular dopamine levels, tended to show a positive correlation with the prolongation of these cognitive states. These findings indicate that dopamine is closely linked to shifts from sensorimotor and perceptual to cognitive brain metastates, potentially underpinning the prioritization of internally oriented over externally driven psychological processes. Our results highlight the importance of dynamic, time-resolved connectivity approaches for understanding neuromodulatory actions in the human brain and suggest that dopamine helps regulate the dynamic balance between functionally competing large-scale brain networks.

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bioRxiv2025

Pharmacological potentiation of Nav1.1 channels in interneurons mitigates tau depositions and neuronal death in a mouse model of neurodegenerative dementias

Epileptiform discharges and neuronal hyperexcitability are key pathophysiological features of Alzheimers disease and related tauopathies. We previously identified selective dynfuntion of parvalbumin-positive GABAergic interneurons (PV neurons), which regulate neural network excitability, in a tauopathy mouse model. However, the mechanistic link between PV neuron deficits, tau pathology, and neurodegeneration remains unclear. Here, we demonstrate that pharmacological enhancement of phasic PV neuron activity markedly attenuates tau accumulation and neuronal loss in a tauopathy mouse model. We developed DSR-143630, a novel activator of voltage-gated sodium channel Nav1.1, selectively expressed in PV neurons. Administration of DSR-143630 alleviated febrile seizures in Nav1.1 haploinsufficient mice and suppressed high-frequency oscillations (HFOs), an electrophysiological signature of hyperexcitability associated with cognitive impairments, in rTg4510 tau transgenic mice. Longitudinal tau PET and volumetric MRI demonstrated that DSR-143630 treatment from 4 to 11 months of age profoundly reduced age-dependent tau deposition and atrophy in the neocortex and hippocampus. Postmortem analyses further revealed decreased levels of phosphorylated tau, preservation of neuronal populations, and attenuated neuroinflammatory responses, including reactive gliosis. These findings establish PV neuron dysfunctions and consequent network hyperexcitability as key drivers of tau pathogenesis and highlight pharmacological Nav1.1 activation as a promising disease-modifying strategy for neurodegenerative tauopathies. One Sentence SummaryPharmacological potentiation of interneuronal activities attenuates aberrant network excitability, progressive tau deposition, and neurodegeneration.

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bioRxiv2024

Longitudinal assessment of DREADD expression and efficacy in the monkey brain

Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) offer a powerful means for reversible control of neuronal activity through systemic administration of inert actuators. Because chemogenetic control relies on DREADD expression levels, understanding and quantifying the temporal dynamics of their expression is crucial for planning long-term experiments in monkeys. In this study, we longitudinally quantified in vivo DREADD expression in macaque monkeys using positron emission tomography with the DREADD-selective tracer [11C]deschloroclozapine (DCZ), complemented by functional studies. Twenty macaque monkeys were evaluated after being injected with adeno-associated virus vectors expressing the DREADDs hM4Di or hM3Dq, whose expression was quantified as changes in [11C]DCZ binding potential from baseline levels. Expression levels of both hM4Di and hM3Dq peaked around 60 days post-injection, remained stable for about 1.5 years, and declined gradually after two years. Significant chemogenetic control of neural activity and behavior persisted for about two years. The presence of protein tags significantly influenced expression levels, with co-expressed protein tags reducing overall expression levels. These findings provide valuable insights and guidelines for optimizing the use of DREADDs in long-term primate studies and potential therapeutic applications.

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bioRxiv2023

Multimodal imaging for validation and optimization of ion channel-based chemogenetics in nonhuman primates

Chemogenetic tools provide an opportunity to manipulate neuronal activity and behavior selectively and repeatedly in nonhuman primates (NHPs) with minimal invasiveness. Designer Receptors Exclusively Activated by Designer Drugs are one example that is based on mutated muscarinic acetylcholine receptors. Another channel-based chemogenetic system available for neuronal modulation in NHPs uses Pharmacologically Selective Actuator Modules (PSAMs), which are selectively activated by Pharmacologically Selective Effector Molecules (PSEMs). To facilitate the use of the PSAM/PSEM system, the selection and dosage of PSEMs should be validated and optimized for NHPs. To this end, we used a multimodal imaging approach. We virally expressed excitatory PSAM (PSAM4-5HT3) in the striatum and the primary motor cortex of two macaque monkeys, and visualized its location through positron emission tomography (PET) with the reporter ligand [18F]ASEM. Chemogenetic excitability of neurons triggered by two PSEMs (uPSEM817 and uPSEM792) was evaluated using [18F]fluorodeoxyglucose-PET imaging, with uPSEM817 being more efficient than uPSEM792. Pharmacological magnetic resonance imaging showed that increased brain activity in the PSAM4-expressing region began approximately 13 min after uPSEM817 administration and continued for at least 60 min. Our multimodal imaging data provide valuable information regarding the manipulation of neuronal activity using the PSAM/PSEM system in NHPs, facilitating future applications. Significance statementLike other chemogenetic tools, the ion channel-based system called Pharmacologically Selective Actuator Module/Pharmacologically Selective Effector Molecule (PSAM/PSEM) allows remote manipulation of neuronal activity and behavior in living animals. Nevertheless, its application in non-human primates (NHPs) is still limited. Here, we used multi-tracer positron emission tomography (PET) imaging and pharmacological magnetic resonance imaging (MRI) to visualize an excitatory chemogenetic ion channel (PSAM4-5HT3) and validate its chemometric function in macaque monkeys. Our results provide the optimal agonist, dose, and timing for chemogenetic neuronal manipulation, facilitating the use of the PSAM/PSEM system and expanding the flexibility and reliability of circuit manipulation in NHPs in a variety of situations.

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bioRxiv2023

In vivo visualization of intracellular pH gradient in brain using PET imaging

Intracellular pH (pHi) is a valuable index for predicting hypoxic brain damage. However, no positron emission tomography (PET) probe is currently available for monitoring pHi in vivo. In this study, we developed a new approach for visualizing monoacylglycerol lipase (MAGL) activity in the brain. This approach used PET with a new probe [11C]HC-A, an azetidine carbamate inhibitor, whose uptake and residence depended on the pHi gradient was evaluated with in silico, in vitro, and in vivo assessments. Molecular dynamics simulations predicted that complex (complex-A) between HC-A and MAGL would be difficult to hydrolyze under acidic conditions. In vitro assessment using rat brain homogenate showed that [11C]HC-A reacted with MAGL to yield [11C]complex-A, which was rapidly hydrolyzed to liberate 11CO2. The 11CO2 liberation rate was slower at lower pH. In PET with [11C]HC-A using ischemic rats, the radioactivity clearance rate, which reflects the production rate of 11CO2 in the brain, was lower in a remarkably hypoxic area than in the contralateral region. In conclusion, we successfully visualized the pHi gradient in the brain using PET imaging.

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bioRxiv2023

Reduced serotonergic transmission alters sensitivity to cost and reward via 5-HT1A and 5-HT1B receptors in monkeys

Deficiency of the serotonin (5-HT) system is considered one of the core biological pathologies of depression and other psychiatric disorders whose key symptom is decreased motivation. Yet, the exact role of 5-HT in motivation remains controversial and elusive. Here, we pharmacologically manipulated the 5-HT system and quantified effects on motivation in terms of incentives and costs for goal-directed action in monkeys. Reversible inhibition of 5-HT synthesis increased refusal responses and reaction times in goal-directed task performance, indicating decreased motivation that could be separated into value-dependent and -independent components. To identify the receptor subtypes involved in these components, we systemically administered antagonists specific for four major 5-HT receptor subtypes: 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT4. Positron emission tomography visualized the unique distribution of each subtype in limbic brain regions and determined the systemic antagonist dose that achieved approximately 30% occupancy. We found that blockade of 5-HT1A, but not other receptor subtypes, increased sensitivity to future workload and time-delay to reward, and decreased motivation in a value-independent manner. Moreover, blocking only 5-HT1B receptors reduced the impact of incentive value on motivation. These results suggest that two distinct processes, mediated by 5-HT1A and 5-HT1B receptors, lead to reduced motivation in 5-HT system deficiency.

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bioRxiv2022

Neural network of superiority illusion predicts the level of dopamine in striatum

In evaluating the personality attributes and performance of the self, people are inclined to view themselves superior to others, a phenomenon known as superiority illusion (SI). This illusive outlook pervades peoples thoughts, creating hope for the future and promoting mental health. Although a specific cortico-striatal functional connectivity (FC) under dopaminergic modulation was previously shown to be implicated in SI, the underlying whole-brain mechanisms have remained unclarified. Herein, to reveal the neural network subserving individuals SI, we conducted a data-driven, machine-learning investigation to explore the resting-state FC network across the whole brain. Using the locally-acquired resting-state functional magnetic resonance imaging data (n = 123), we identified a set of 15 FCs most informative in classifying individuals with higher-versus lower-than-average levels of SI in evaluating positive trait words (area under the curve [AUC] = 0.81). Among the 15 FCs, the contribution level to the classification was 11% by the previously-highlighted cortico-striatal FC alone, but 60% by the encompassing cortico-limbico-striatal network cluster. A newly-identified, cortico-thalamic FC and another FC cluster also demonstrated substantial contribution. The classification accuracy was generalized into an independent cohort (n = 36; AUC = 0.73). Importantly, using the same set of 15 FCs, we achieved prediction on an individuals level of striatal dopamine D2 receptor availability (Pearson correlation, r = 0.46, P = 0.005). This is the first successful identification of the whole-brain neural network that simultaneously predicts the behavioral manifestation and molecular underpinning of an essential psychological process that promotes well-being and mental health. Significance StatementSuperiority illusion (SI) is a basic self-referential framework that pervades peoples thoughts and promotes well-being and mental health. An aberrant form of SI has been reported in psychiatric conditions such as depression. Our hypothesis-free, data-driven investigation revealed the spatially-distributed neural network that for the first time achieved prediction on an individuals levels of SI and the striatal dopaminergic transmission simultaneously. In principle, this multiple-biological-layer framework can be applicable to any behavioral trait to establish a link with its underlying neural network and neurochemical properties, which could quantitatively present the relation of its aberrant form with the pathophysiology of neuropsychiatric disorders. Future clinical research may aid in deriving a diagnostic biomarker for examining the related behavioral and neurochemical characteristics within individuals.

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bioRxiv2021

Serotonergic neural network related to behavioral inhibition system

Rationale The tendency to avoid punishment, called behavioral inhibition system, is an essential aspect of motivational behavior. Behavioral inhibition system is related to negative affect, such as anxiety, depression and pain, but its neural basis has not yet been clarified. Objectives To clarify the association between individual variations in behavioral inhibition system and brain 5-HT2A receptor availability and specify which brain networks were involved in healthy male subjects, using [18F]altanserin positron emission tomography and resting-state functional magnetic resonance imaging. Results Behavioral inhibition system score negatively correlated with 5-HT2A receptor availability in anterior cingulate cortex. A statistical model indicated that the behavioral inhibition system score was associated with 5-HT2A receptor availability, which was mediated by the functional connectivity between anterior cingulate cortex and left middle frontal gyrus, both of which involved in the cognitive control of negative information processing. Conclusions Individuals with high behavioral inhibition system displays low 5-HT2A receptor availability in anterior cingulate cortex and this cognitive control network links with prefrontal-cingulate integrity. These findings have implications for underlying the serotonergic basis of physiologies in aversion.

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bioRxiv2021

Radiosynthesis and preclinical evaluation of a carbon-11 labeled PDE7 inhibitor for PET neuroimaging

BackgroundDysfunction of cyclic nucleotide phosphodiesterase 7 (PDE7) has been associated with excess intracellular cAMP concentrations, fueling pathogenic processes that are implicated in neurodegenerative disorders. The aim of this study was to develop a suitable PDE7-targeted positron emission tomography (PET) probe that allows non-invasive mapping of PDE7 in the mammalian brain. MethodsBased on a spiro cyclohexane-1,4-quinazolinone scaffold with known inhibitory properties towards PDE7, we designed and synthesized a methoxy analog that was suitable for carbon-11 labeling. Radiosynthesis was conducted with the respective desmethyl precursor using [11C]MeI. The resulting PET probe, codenamed [11C]26, was evaluated by cell uptake studies, ex vivo biodistribution and radiometabolite studies, as well as in vivo PET experiments in rodents and nonhuman primates (NHP). ResultsTarget compound 26 and the corresponding phenolic precursor were synthesized in 2-3 steps with overall yields of 49.5% and 12.4%, respectively. An inhibitory constant (IC50) of 31 nM towards PDE7 was obtained and no significant interaction with other PDE isoforms were observed. [11C]26 was synthesized in high molar activities (170 - 220 GBq/{micro}mol) with radiochemical yields of 34{+/-}7%. In vitro cell uptake of [11C]26 was 6-7 folds higher in PDE7 overexpressing cells, as compared to the controls, whereas an in vitro specificity of up to 90% was measured. Ex vivo metabolite studies revealed a high fraction of intact parent in the rat brain (98% at 5 min and 75% at 30 min post injection). Considerable brain penetration was further corroborated by ex vivo biodistribution and PET imaging studies - the latter showing heterogenic brain uptake. While marginal specific binding was observed by PET studies in rodents, a moderate, but dose-dependent, blockade was observed in the NHP brain following pretreatment with non-radioactive 26. ConclusionIn this work, we report on the preclinical evaluation of [11C]26 (codename [11C]P7-2104), a PDE7-targeted PET ligand that is based on a spiroquinazolinone scaffold. [11C]26 displayed promising in vitro performance characteristics, a moderate degree of specific binding in PET studies with NHP. Accordingly, [11C]26 will serve as a valuable lead compound for the development of a new arsenal of PDE7-targeted probes with potentially improved in vivo specificity.

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bioRxiv2020

Tracking tau fibrillogenesis and consequent primary phagocytosis of neurons mediated by microglia in a living tauopathy model

Fibrillary tau pathologies have been implicated in Alzheimers and allied neurodegenerative diseases, while mechanisms by which neurons bearing tau tangles die remain enigmatic. To address this issue, we pursued tau and related key pathologies macroscopically by PET and MRI and microscopically by intravital two-photon laser optics. Time-course macroscopic assays of tau transgenic mice demonstrated intimate associations of tau deposition and increase of an inflammatory microglial marker, translocator protein (TSPO), with regional brain atrophy. Longitudinal microscopy of these mice revealed a rapid turnover of tau lesions resulting from continuous generation of new tau aggregates followed by loss of neurons and their fibrillar contents. This technology also allowed the capturing of the disappearance of tangle-bearing neurons several days after being engulfed by activated microglia. Notably, a therapeutic TSPO ligand profoundly suppressed the mobility and phagocytotic activity of microglia and improved neuronal survival in this model, supporting the involvement of primary phagocytosis of viable neurons by microglia in tau-primed neuronal death. Finally, partial depletion of microglia revealed roles of immune factors, MFG-E8 and C1q, as eat-me signals for an immediate attraction of phagocytic microglia towards the elimination of tangle-loaded neurons.

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bioRxiv2020

Synthesis and preclinical evaluation of MTP38 as a novel PET ligand for phophodiesterase 7 in the brain

PurposePhosphodiesterase (PDE) 7 is a potential therapeutic target for neurological and inflammatory diseases, although in-vivo visualization of PDE7 has not been successful. In this study, we aimed to develop [11C]MTP38 as a novel positron emission tomography (PET) ligand for PDE7. Methods[11C]MTP38 was radiosynthesized by 11C-cyanation of a bromo precursor with [11C]HCN. PET scans of rat and rhesus monkey brains and in-vitro autoradiography of brain sections derived from these species were conducted with [11C]MTP38. In monkeys, dynamic PET data were analyzed with an arterial input function to calculate the total distribution volume (VT). The non-displaceable binding potential (BPND) in the striatum was also determined by a reference tissue model with cerebellar reference. Finally, striatal occupancy of PDE7 by an inhibitor was calculated in monkeys according to changes in BPND. Results[11C]MTP38 was synthesized with radiochemical purity [≥] 99.4% and molar activity of 38.6 {+/-} 12.6 GBq/mol. Autoradiography revealed high radioactivity in the striatum and its reduction by non-radiolabeled ligands, in contrast with unaltered autoradiographic signals in other regions. In-vivo PET after radioligand injection to rats and monkeys demonstrated that radioactivity was rapidly distributed to the brain and intensely accumulated in the striatum relative to the cerebellum. Correspondingly, estimated VT values in the monkey striatum and cerebellum were 3.59 and 2.69 mL/cm3, respectively. The cerebellar VT value was unchanged by pretreatment with unlabeled MTP38. Striatal BPND was reduced in a dose-dependent manner after pretreatment with MTP-X, a PDE7 inhibitor. Relationships between PDE7 occupancy by MTP-X and plasma MTP-X concentration could be described by Hills sigmoidal function. ConclusionWe have provided the first successful preclinical demonstration of in-vivo PDE7 imaging with a specific PET radioligand. [11C]MTP38 is a feasible radioligand for evaluating PDE7 in the brain and is currently being applied to a first-in-human PET study.

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bioRxiv2020

In vivo visualization of propagating α-synuclein pathologies in mouse and marmoset models by a bimodal imaging probe, C05-05

Deposition of -synuclein fibrils is implicated in Parkinsons disease (PD) and dementia with Lewy bodies (DLB), while in vivo detection of -synuclein pathologies in these illnesses has been challenging. Here, we have developed a small-molecule ligand, C05-05, for visualizing -synuclein deposits in the brains of living subjects. In vivo optical and positron emission tomography (PET) imaging of mouse and marmoset models demonstrated that C05-05 captured a dynamic propagation of fibrillogenesis along neural pathways followed by disruptions of these structures. High-affinity binding of 18F-C05-05 to -synuclein aggregates in human brain tissues was also proven by in vitro assays. Notably, PET-detectable 18F-C05-05 signals were intensified in the midbrains of PD and DLB patients as compared to healthy controls, providing the first demonstration of visualizing -synuclein pathologies in these illnesses. Collectively, we propose a new imaging technology offering neuropathology-based translational assessments of PD and allied disorders towards diagnostic and therapeutic research and development.

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bioRxiv2020

Genetically targeted reporter imaging of deep neuronal network in the mammalian brain

Positron Emission Tomography (PET) allows biomolecular tracking, while PET monitoring of brain networks has been hampered by the lack of a suitable reporter. Here, we describe in vivo brain imaging that takes advantage of bacterial dihydrofolate reductase, ecDHFR, and its unique antagonist, TMP. In mice, peripheral administration of radiofluorinated and fluorescent TMP analogs enabled PET and intravital microscopy, respectively, of neuronal ecDHFR expressions. This technique is applicable to the visualization of neuronal ensemble activities elicited by chemogenetic manipulation in the mouse hippocampus. Notably, ecDHFR-PET offers mapping of neuronal projections in non-human primate brains, indicating the availability of ecDHFR-based tracking technologies for network monitoring. Finally, we demonstrate the utility of TMP analogs for PET assays of turnover and self-assembly of proteins tagged with ecDHFR mutants. Our findings may facilitate a broad spectrum of PET analyses of a mammalian brain circuit at molecular levels that were not previously applicable for technical reasons.

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bioRxiv2019

Deschloroclozapine: a potent and selective chemogenetic actuator enables rapid neuronal and behavioral modulations in mice and monkeys

The chemogenetic technology Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) affords remotely reversible control of cellular signaling, neuronal activity and behavior. Although the combination of muscarinic-based DREADDs with clozapine-N-oxide (CNO) has been widely used, sluggish kinetics, metabolic liabilities, and potential off-target effects of CNO represent areas for improvement. Here we provide a new high affinity and selective agonist deschloroclozapine (DCZ) for muscarinic-based DREADDs. Positron emission tomography revealed that DCZ selectively bound to and occupied DREADDs in both mice and monkeys. Systemic delivery of low doses of DCZ (1 or 3 g/kg) enhanced neuronal activity via hM3Dq within minutes in mice and monkeys. Intramuscular injections of DCZ (100 g/kg) reversibly induced spatial working memory deficits in monkeys expressing hM4Di in the prefrontal cortex. DCZ represents the most potent, selective, metabolically stable and fast-acting DREADD agonist reported with utility in both mice and non-human primates for a variety of applications.

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