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-Noxide (CNO) has been widely used, sluggish kinetics, metabolic liabilities, and potential offtarget 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 μg/kg) enhanced neuronal activity via hM3Dq within minutes in mice and monkeys. Intramuscular injections of DCZ (100 μg/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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A panel of radiochemicals has enabled in-vivo positron emission tomography (PET) of tau pathologies in Alzheimer′s disease (AD), while sensitive detection of frontotemporal lobar degeneration (FTLD) tau inclusions has been unsuccessful. Here, we generated an imaging probe, PM-PBB3, for capturing diverse tau deposits. In-vitro assays demonstrated the reactivity of this compound with tau pathologies in AD and FTLD. We could also utilize PM-PBB3 for optical/PET imaging of a living murine tauopathy model. A subsequent clinical PET study revealed increased binding of 18F-PM-PBB3 in diseased patients, reflecting cortical-dominant AD and subcortical-dominant PSP tau topologies. Notably, the in-vivo reactivity of 18F-PM-PBB3 with FTLD tau inclusion was strongly supported by neuropathological examinations of autopsied and biopsied brains derived from Pick′s disease, PSP and corticobasal degeneration patients who underwent PET scans. Finally, visual inspection of 18F-PM-PBB3-PET images was indicated to facilitate individually based identification of diverse clinical phenotypes of FTLD on the neuropathological basis.

The chemogenetic technology, Designer Receptors Exclusively Activated by Designer Drugs (DREADDs), affords reversible and remote control of cellular signaling, neuronal activity and behavior. Although the combination of muscarinic-based DREADDs with clozapine-N-oxide (CNO) has been widely used, the sluggish kinetics, metabolic liabilities, and potential for off-target effects of CNO represent areas for improvement. Here we provide a new agonist deschloroclozapine (DCZ), which displays high affinity and selectivity 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 μ g/kg) enhanced neuronal activity via hM 3 Dq within minutes in mice and monkeys. Intramuscular injection of DCZ (100 μ g/kg) reversibly induced behavioral deficits in hM 4 Di-expressing monkeys.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. 7 at dopaminergic (D 1 and D 2 ) and serotonergic (5-HT 2A and 5-HT 2C ) receptors compared with clozapine 14 . We determined that DCZ has 100-fold improved affinity and stronger agonist potency for hM 3 Dq and hM 4 Di relative to CNO or C21, while reducing off-target binding compared with clozapine in vitro. Using positron emission tomography (PET), we demonstrated that DCZ rapidly penetrates into the brain and selectively binds to DREADDs, and that DCZ doses for DREADD occupancy are 20-and 60-fold smaller than CNO and C21,respectively. Finally, we demonstrated that DCZ is capable of rapidly (<10 min post-injection) activating hM 3 Dq and hM 4 Di in both mice and monkeys without discernible off-target action. Thus, DCZ represents a potent and selective chemogenetic actuator for muscarinic-based DREADDs in mice and primates that is useful for a variety of in vitro and in vivo contexts with high translational potential. 8 RESULTS DCZ selectively binds to DREADDs in vitro and in vivoWe first assessed the binding affinities of DCZ to hM 3 Dq and hM 4 Di, and compared them to those of clozapine, CNO and C21 using radioligand competition binding assays. DCZ inhibited [ 3 H]quinuclidinyl benzilate (QNB) binding to hM 3 Dq and hM 4 Di with nanomolar affinity (inhibition constants; hM3Dq K i = 6.3 nM; hM4Di K i = 4.2 nM), which was comparable to clozapine ( hM3Dq K i = 5.9 nM; hM4Di Ki = 0.89), while CNO and C21 were about 100-and 50-fold weaker, respectively (CNO, hM3Dq K i = 680 nM; hM4Di K i = 360 nM; C21, hM3Dq K i = 850 nM; hM4Di K i = 180 nM)( Table 1). Unlike clozapine ( Fig. 1c and Supplementary Table 1), DCZ had negligible affinities for a large number of tested G protein-coupled receptors (GPCRs), ion channels or transporters (K i 's > 100 nM) and relatively low affinities for a few endogenous receptors such as muscarinic acetylcholine ( hM1 K i = 83 nM; hM5 K i = 55 nM) and serotonin receptors ( 5-HT2A K i = 87 nM)( Fig. 1b and Supplement...

Intake of specific seven essential amino acids affects the pathology of the brain.

No abstract

Deposition of intracellular α-synuclein fibrils is implicated in neurodegenerative parkinsonian disorders, while high-contrast in vivo detection of α-synuclein depositions has been unsuccessful in animal models and humans. Here, we have developed a bimodal imaging probe, C05-05, for visualizing α-synuclein inclusions in the brains of living animals modeling α-synuclein propagation. In vivo optical and PET imaging of a mouse model demonstrated sensitive detection of α-synuclein aggregates by C05-05, revealing a dynamic propagation of fibrillogenesis along neural pathways followed by disruptions of these structures. Moreover, longitudinal 18F-C05-05-PET of a marmoset model captured widespread dissemination of fibrillary pathologies accompanied by neurodegeneration detected by dopamine transporter PET. In addition, in vitro assays demonstrated the high-affinity binding of 18F-C05-05 to α-synuclein versus other protein pathologies in human brain tissues. Collectively, we propose a new imaging technology enabling etiological and therapeutic assessments of α-synuclein pathogenesis at nonclinical levels, highlighting the applicability of C05-05 to clinical PET.

To assess if magnetic resonance spectroscopy (MRS)-measured Glutamate (Glu) and GABA reflect excitatory and inhibitory neural activities, respectively, we conducted MRS measurements along with two-photon mesoscopic imaging of calcium signals in excitatory and inhibitory neurons of living, unanesthetized mice. For monitoring stimulus-driven activations of a brain region, MRS signals and mesoscopic neural activities were measured during two consecutive sessions of 15-min prolonged sensory stimulations. In the first session, putative excitatory neuronal activities were increased, while inhibitory neuronal activities remained at the baseline level. In the second half, while excitatory neuronal activities remained elevated, inhibitory neuronal activities were significantly enhanced. We assessed regional neurochemical statuses by measuring MRS signals, which were overall in accordance with the neural activities, and neuronal activities and neurochemical statuses in a mouse model of Dravet syndrome under resting condition. Mesoscopic assessments showed that activities of inhibitory neurons in the cortex were diminished relative to wild-type mice in contrast to spared activities of excitatory neurons. Consistent with these observations, the Dravet model exhibited lower concentrations of GABA than wild-type controls. Collectively, the current investigations demonstrate that MRS-measured Glu and GABA can reflect spontaneous and stimulated activities of neurons producing and releasing these neurotransmitters in an awake condition.