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Metabolically derived clozapine is the in vivo actuator of designer drug receptors expressed in the central nervous system.

Abstract. Recently, we created a family of engineered G protein-coupled receptors (GPCRs) called DREADD (designer receptors exclusively activated by designer dr

Addgene's guide to using Chemogenetics plasmids in your lab for interrogation of neuronal activity.

A new tool called Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) allows us to hijack cell signaling to study cell function.

Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) represent a technical revolution in integrative neuroscience. However, the first used ligands exhibited dose-dependent selectivity for their molecular target, leading to potential unspecific effects. Compound 21 (C21) was recently proposed as an alternative, but in vivo characterization of its properties is not sufficient yet. Here, we evaluated its potency to selectively modulate the activity of nigral dopaminergic (DA) neurons through the canonical DREADD receptor hM4Di using TH-Cre rats. In males, 1 mg.kg-1 of C21 strongly increased nigral neurons activity in control animals, indicative of a significant off-target effect. Reducing the dose to 0.5 mg.kg-1 circumvented this unspecific effect, while activated the inhibitory DREADDs and selectively reduced nigral neurons firing. In females, 0.5 mg.kg-1 of C21 induced a transient and residual off-target effect that may mitigated the inhibitory DREADDs-mediated effect. This study raises up the necessity to test selectivity and efficacy of chosen ligands for each new experimental condition.

During the past few years, CNO-sensitive designer G protein-coupled receptors (GPCRs) known as DREADDs ( designer receptors exclusively activated by designer drugs) have emerged as powerful new tools...

Designer receptors exclusively activated by designer drugs (DREADDs) are an advanced experimental tool that could potentially provide a novel approach to pain management. In particular, expression of an inhibitory (Gi-coupled) DREADD in nociceptors might enable ligand-dependent analgesia. To test this possibility, TRPV1-cre mice were used to restrict expression of Gi-DREADDs to predominantly C-fibers. Whereas baseline heat thresholds in both male and female mice expressing Gi-DREADD were normal, 1 mg/kg clozapine- N -oxide (CNO) produced a significant 3 h increase in heat threshold that returned to baseline by 5 h after injection. Consistent with these behavioral results, CNO decreased action potential firing in isolated sensory neurons from Gi-DREADD mice. Unexpectedly, however, the expression of Gi-DREADD in sensory neurons caused significant changes in voltage-gated Ca2+ and Na+ currents in the absence of CNO, as well as an increase in Na+ channel (NaV1.7) expression. Furthermore, CNO-independent excitatory and inhibitory second-messenger signaling was also altered in these mice, which was associated with a decrease in the analgesic effect of endogenous inhibitory G-protein-coupled receptor activation. These results highlight the potential of this exciting technology, but also its limitations, and that it is essential to identify the underlying mechanisms for any observed behavioral phenotypes. SIGNIFICANCE STATEMENT DREADD technology is a powerful tool enabling manipulation of activity and/or transmitter release from targeted cell populations. The purpose of this study was to determine whether inhibitory DREADDs in nociceptive afferents could be used to produce analgesia, and if so, how. DREADD activation produced a ligand-dependent analgesia to heat in vivo and a decrease in neuronal firing at the single-cell level. However, we observed that expression of Gi-DREADD also causes ligand-independent changes in ion channel activity and second-messenger signaling. These findings highlight both the potential and the limitations of this exciting technology as well as the necessity to identify the mechanisms underlying any observed phenotype.

Designer receptors help understand cellular signals and could treat epilepsy and Parkinson's disease, but need new tools, finds Andy Extance

Spinal cord injury (SCI) often damages, not only white matter axon tracts that transmits signals to and from the brain, but also the central gray matter, causin...

Despite years of study, current treatments do not sufficiently treat chronic pain syndromes. Electrical brain stimulation of the periaqueductal gray (PAG) produces profound antinociception, and shows promise in treating these difficult conditions. However, this treatment can also produce intense anxiety which has limited its use. The goal of this study was to better define the complex neural circuitry in the PAG specifically responsible for the analgesic effect and hypothesized that in targeting specific neural circuits we would be able to produce analgesia without anxiety.

Obesity, a condition affecting more than one in three American adults, is associated with hypothalamic neuronal injury, inflammation, and gliosis- a process characterized by accumulation of activated microglia. Experimental evidence from our lab suggests that microglial activation and inflammatory signaling play a functional role in obesity pathogenesis and, furthermore, that this inflammation, or the blockade of such, may affect whole-body glucose homeostasis. Microglial-specific NF-kB knock-out mice are protected from diet-induced obesity, but, despite their lean phenotype, develop glucose intolerance similar to wild type controls. We therefore used stimulatory (hM3Dq) and inhibitory (hM4Di) DREADDs to test the hypothesis that microglial activation or inactivation acutely affects systemic glucose homeostasis. We generated novel mouse models that selectively express the hM3Dq- and hM4Di-DREADD transgenes in microglia. Expression was verified via qRT-PCR, flow cytometry, and IHC. Cohorts of mice and littermate controls were maintained on either normal chow diet or high-fat diet (HFD). Glucose tolerance tests were performed on mice following administration of the DREADD receptor agonist clozapine-N-oxide (CNO). Acute microglial activation via CNO administration in hM3Dq-DREADD animals improved glucose tolerance under both chow and HFD conditions. Acute CNO-induced microglial inactivation in hM4Di-DREADD animals increased fasting glucose in chow-fed animals and worsened glucose tolerance in HFD-fed animals. These findings provide the first evidence that peripheral glucose homeostasis is affected by microglial activity and inflammatory signaling and can be manipulated on an acute timescale using DREADD technology. Disclosure K.M. Ness: None. J. Douglass: None. M. Valdearcos-Contreras: None. M.D. Dorfman: None. A. Niraula: None. S.K. Koliwad: Consultant; Self; AstraZeneca. Stock/Shareholder; Self; Suggestic, Yes Health. J. Thaler: None. Funding National Institutes of Health (T32DK007247, R01DK119754)

Scientific Text Article | Here we describe two non-invasive methods to chronically control neuronal activity using chemogenetics in mice. Eye-drops were used to...

Designer receptors exclusively activated by designer drugs (DREADDs) modify cellular activity following administration of the exogenous ligand clozapine-N-oxide (CNO). However, some reports indicate CNO may have off-target effects. The current studies investigate the use of Gq DREADDs in CaMKIIa-expressing neurons in the median preoptic nucleus (MnPO). Male Sprague-Dawley rats (250 g) anesthetized with isoflurane were stereotaxically microinjected in the MnPO with the Gq DREADD (AAV5-CaMKIIa-HM3D-mCherry) or control virus (AAV5-CaMKIIa-mCherry). Following a 2-wk recovery, rats were used for either immunohistochemical Fos analysis or in vitro patch-clamp electrophysiology. In Gq DREADD-injected rats, CNO induced significant increases in Fos staining in the MnPO and in regions that receive direct or indirect projections from the MnPO. In electrophysiological studies, CNO depolarized and augmented firing frequency in both Gq DREADD-positive neurons (Gq DREADD) as well as unlabeled MnPO neurons in slices from Gq DREADD-injected rats (Gq DREADDx). Gq DREADDx neurons also displayed increases in spontaneous postsynaptic current (sPSC) frequency in response to CNO. Additionally, CaMKIIa-positive MnPO neurons, which also express nitric oxide synthase (NOS), were treated with Nω-nitro-l-arginine (l-NNA; competitive inhibitor of NOS) and hemoglobin (NO scavenger) to assess the role of NO in Gq DREADDx neuron recruitment. Both l-NNA and hemoglobin blocked CNO-induced effects in Gq DREADDx neurons without affecting Gq DREADD neurons. These findings indicate that Gq DREADD-mediated activation of CaMKIIa/NOS expressing neurons in the MnPO can influence the activity of neighboring neurons. Future studies utilizing the use of Gq DREADDs will need to consider the potential recruitment of additional cell populations. NEW & NOTEWORTHY Rats were injected in the median preoptic nucleus (MnPO) with either an adeno-associated virus (AAV) and excitatory (Gq) designer receptor exclusively activated by designer drugs (DREADD) construct or a control AAV. In the Gq DREADD-injected rats only, clozapine-N-oxide (CNO) increased Fos staining in the MnPO and its targets and increased neuron action potential frequency. In electrophysiology experiments with slices with DREADD cells, unlabeled cells were activated and this was likely due to nitric oxide release by the DREADD cells.

Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) are genetically modified G-protein-coupled receptors (GPCRs), that can be activated by...

Chemogenetics is a fairly new area of neuroscience that explores the use of synthetically derived receptors and selective ligands to temporarily activate or deactivate specific brain areas. These receptors ...

Hundreds of hormones and ligands stimulate cyclic AMP (cAMP) signaling in different tissues through the activation of G-protein-coupled receptors (GPCRs). Although the functions and individual effectors of cAMP signaling are well characterized in ...

The designer receptors exclusively activated by designer drugs (DREADD) system can be used to suppress nociceptors, resulting in analgesia to heat, reports a new mouse study. But thanks to a set of careful control experiments, researchers led by Brian Davis and Michael Gold, University of Pittsburgh, US, also find an important caveat: DREADD expression alters endogenous channel activity and signaling pathways in sensory neurons independent of the ligand used to activate the receptor.

Evolving research on Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) may someday lead to new therapies for treatment-resistant neuropsychiatric disorders.

The fruitless, decade-long search for DREADDs has a silver lining

[En Español] There are few things I find more satisfying than a good acronym, and DREADD  or Designer Receptor Exclusively Activated by a Designer Drug has got to be my favorite.  The name is just …