Select publications from the Biobehavioral Imaging and Molecular Neuropsychopharmacology Unit.
Michaelides, Michael; Miller, Michael L; Egervari, Gabor; Primeaux, Stefany D; Gomez, Juan L; Ellis, Randall J; Landry, Joseph A; Szutorisz, Henrietta; Hoffman, Alexander F; Lupica, Carl R; Loos, Ruth J F; Thanos, Panayotis K; Bray, George A; Neumaier, John F; Zachariou, Venetia; Wang, Gene-Jack; Volkow, Nora D; Hurd, Yasmin L
In: Molecular Psychiatry, 25 (9), pp. 2058–2069, 2020, ISBN: 1476-5578.
Consumption of high fat, high sugar (western) diets is a major contributor to the current high levels of obesity. Here, we used a multidisciplinary approach to gain insight into the molecular mechanisms underlying susceptibility to diet-induced obesity (DIO). Using positron emission tomography (PET), we identified the dorsal striatum as the brain area most altered in DIO-susceptible rats and molecular studies within this region highlighted regulator of G-protein signaling 4 (Rgs4) within laser-capture micro-dissected striatonigral (SN) and striatopallidal (SP) medium spiny neurons (MSNs) as playing a key role. Rgs4 is a GTPase accelerating enzyme implicated in plasticity mechanisms of SP MSNs, which are known to regulate feeding and disturbances of which are associated with obesity. Compared to DIO-resistant rats, DIO-susceptible rats exhibited increased striatal Rgs4 with mRNA expression levels enriched in SP MSNs. siRNA-mediated knockdown of striatal Rgs4 in DIO-susceptible rats decreased food intake to levels comparable to DIO-resistant animals. Finally, we demonstrated that the human Rgs4 gene locus is associated with increased body weight and obesity susceptibility phenotypes, and that overweight humans exhibit increased striatal Rgs4 protein. Our findings highlight a novel role for involvement of Rgs4 in SP MSNs in feeding and DIO-susceptibility.
Bonaventura, Jordi; Eldridge, Mark A G; Hu, Feng; Gomez, Juan L; Sanchez-Soto, Marta; Abramyan, Ara M; Lam, Sherry; Boehm, Matthew A; Ruiz, Christina; Farrell, Mitchell R; Moreno, Andrea; Faress, Islam Mustafa Galal; Andersen, Niels; Lin, John Y; Moaddel, Ruin; Morris, Patrick J; Shi, Lei; Sibley, David R; Mahler, Stephen V; Nabavi, Sadegh; Pomper, Martin G; Bonci, Antonello; Horti, Andrew G; Richmond, Barry J; Michaelides, Michael
In: Nat Commun, 10 (1), pp. 4627, 2019, ISSN: 2041-1723 (Electronic); 2041-1723 (Linking).
Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) are a popular chemogenetic technology for manipulation of neuronal activity in uninstrumented awake animals with potential for human applications as well. The prototypical DREADD agonist clozapine N-oxide (CNO) lacks brain entry and converts to clozapine, making it difficult to apply in basic and translational applications. Here we report the development of two novel DREADD agonists, JHU37152 and JHU37160, and the first dedicated (18)F positron emission tomography (PET) DREADD radiotracer, [(18)F]JHU37107. We show that JHU37152 and JHU37160 exhibit high in vivo DREADD potency. [(18)F]JHU37107 combined with PET allows for DREADD detection in locally-targeted neurons, and at their long-range projections, enabling noninvasive and longitudinal neuronal projection mapping.
Volkow, Nora D; Michaelides, Michael; Baler, Ruben
The Neuroscience of Drug Reward and Addiction Journal Article
In: Physiological Reviews, 99 (4), pp. 2115-2140, 2019, (PMID: 31507244).
Drug consumption is driven by a drug's pharmacological effects, which are experienced as rewarding, and is influenced by genetic, developmental, and psychosocial factors that mediate drug accessibility, norms, and social support systems or lack thereof. The reinforcing effects of drugs mostly depend on dopamine signaling in the nucleus accumbens, and chronic drug exposure triggers glutamatergic-mediated neuroadaptations in dopamine striato-thalamo-cortical (predominantly in prefrontal cortical regions including orbitofrontal cortex and anterior cingulate cortex) and limbic pathways (amygdala and hippocampus) that, in vulnerable individuals, can result in addiction. In parallel, changes in the extended amygdala result in negative emotional states that perpetuate drug taking as an attempt to temporarily alleviate them. Counterintuitively, in the addicted person, the actual drug consumption is associated with an attenuated dopamine increase in brain reward regions, which might contribute to drug-taking behavior to compensate for the difference between the magnitude of the expected reward triggered by the conditioning to drug cues and the actual experience of it. Combined, these effects result in an enhanced motivation to ``seek the drug'' (energized by dopamine increases triggered by drug cues) and an impaired prefrontal top-down self-regulation that favors compulsive drug-taking against the backdrop of negative emotionality and an enhanced interoceptive awareness of ``drug hunger.'' Treatment interventions intended to reverse these neuroadaptations show promise as therapeutic approaches for addiction.
Magnus, Christopher J; Lee, Peter H; Bonaventura, Jordi; Zemla, Roland; Gomez, Juan L; Ramirez, Melissa H; Hu, Xing; Galvan, Adriana; Basu, Jayeeta; Michaelides, Michael; Sternson, Scott M
In: Science, 364 (6436), 2019, ISSN: 0036-8075.
Targeting ligand-responsive receptors to specific groups of cells, a strategy known as chemogenetics, is a powerful tool in many neurological applications. There is increasing interest in extending these tools for human treatment. Magnus et al. designed chemogenetic ion channels that improve currently available systems and are activated by the clinically used antismoking drug varenicline. They engineered a ligand-binding domain less responsive to endogenous signals and identified agonists that function at nanomolar concentrations. The combination of drug and introduced channels transiently silenced neurons, with slow but effective washout, and induced behavioral changes in animal models after brain administration.Science, this issue p. eaav5282INTRODUCTIONLocalized control of neuron activity is important for both brain research and therapy. Chemogenetics is a method to control cellular activity by targeting defined cell populations with an exogenous receptor that is engineered to respond selectively to a small-molecule agonist. The approach is generalizable because a receptor-agonist combination can be used to activate or inhibit different neural populations in any brain region. Moreover, using agonists that are selective for the chemogenetic receptor allows cell type–specific modulation, in contrast to traditional pharmacology. Chemogenetic tools have achieved widespread utility in animal models, and there is growing interest in developing chemogenetic systems that are suitable for human therapeutic applications.RATIONALEOptimally, a chemogenetic system should have several characteristics for use in the nervous system: (i) The introduced receptor should be activated by low agonist doses; (ii) human use would be facilitated by a chemogenetic agonist that is already a safe and well-tolerated clinically approved drug that crosses the blood-brain barrier, whereas for research applications the agonist should be highly selective for the chemogenetic receptor over endogenous targets; (iii) chemogenetic receptors should be inert in the absence of the drug, lacking constitutive activity or responsiveness to endogenous ligands; (iv) the receptors should activate or inhibit neurons efficaciously, durably, and reversibly; and (v) the site and level of expression of the chemogenetic receptor should be measurable noninvasively. Existing chemogenetic systems did not fulfill all these criteria.RESULTSWe identified mutations of the ligand-binding domain of the α7 nicotinic acetylcholine receptor that conferred potent activity to the FDA-approved smoking cessation drug varenicline. We created chimeric ligand-gated ion channels by combining these modified ligand-binding domains with ion pore domains from either the glycine receptor or the serotonin 3 receptor, which conduct chloride or cations, respectively. These two types of chemogenetic channels inhibit or activate neurons upon binding varenicline at concentrations below those used clinically to treat nicotine addiction. Varenicline is especially attractive for potential therapeutic applications because it shows limited metabolism, durable pharmacokinetics, and high oral and brain bioavailability. Chemogenetic inhibition or activation was sustained for at least 2 to 3 weeks of continual exposure to varenicline, indicating suitability for chronic use. Expression of the chemogenetic ion channels was visualized in animals by positron emission tomography, enabling noninvasive measurement of the expression and anatomic site of chemogenetic receptors. We showed robust responses to chemogenetic silencing of neurons using low doses of varenicline in mice and one monkey. Finally, we synthesized brain-penetrant analogs of varenicline with subnanomolar potency and with greatly enhanced selectivity for the chemogenetic receptors that were effective for modulation of neural activity in mice.CONCLUSIONWe developed a toolbox of modular ion channels and selective, ultrapotent agonists that can be used for targeted control of brain activity in rodent and primate models. Additional studies will be needed to establish long-term safety and efficacy with chemogenetic receptors for therapeutic applications, but this is facilitated by using varenicline. These chemogenetic technologies can advance research into neural circuit disorders while enabling extension to human therapies.Chemogenetics for mice, monkeys, and potential therapy in humans.Modular ion channels were engineered to be activated by ultrapotent agonists, which selectively inhibit or excite activity in neurons expressing the chemogenetic receptors (blue). Neuron modulation was characterized by calcium imaging, electrophysiology, and behavior in mice and a monkey. These chemogenetic receptors and their FDA-approved agonists may facilitate translation of chemogenetics to therapies for human neurological diseases.Chemogenetics enables noninvasive chemical control over cell populations in behaving animals. However, existing small-molecule agonists show insufficient potency or selectivity. There is also a need for chemogenetic systems compatible with both research and human therapeutic applications. We developed a new ion channel–based platform for cell activation and silencing that is controlled by low doses of the smoking cessation drug varenicline. We then synthesized subnanomolar-potency agonists, called uPSEMs, with high selectivity for the chemogenetic receptors. uPSEMs and their receptors were characterized in brains of mice and a rhesus monkey by in vivo electrophysiology, calcium imaging, positron emission tomography, behavioral efficacy testing, and receptor counterscreening. This platform of receptors and selective ultrapotent agonists enables potential research and clinical applications of chemogenetics.
Michaelides, Michael; Miller, Michael L; DiNieri, Jennifer A; Gomez, Juan L; Schwartz, Elizabeth; Egervari, Gabor; Wang, Gene Jack; Mobbs, Charles V; Volkow, Nora D; Hurd, Yasmin L
In: Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 42 (12), pp. 2365–2376, 2017, ISBN: 1740-634X; 0893-133X.
Appetitive drive is influenced by coordinated interactions between brain circuits that regulate reinforcement and homeostatic signals that control metabolism. Glucose modulates striatal dopamine (DA) and regulates appetitive drive and reinforcement learning. Striatal DA D2 receptors (D2Rs) also regulate reinforcement learning and are implicated in glucose-related metabolic disorders. Nevertheless, interactions between striatal D2R and peripheral glucose have not been previously described. Here we show that manipulations involving striatal D2R signaling coincide with perseverative and impulsive-like responding for sucrose, a disaccharide consisting of fructose and glucose. Fructose conveys orosensory (ie, taste) reinforcement but does not convey metabolic (ie, nutrient-derived) reinforcement. Glucose however conveys orosensory reinforcement but unlike fructose, it is a major metabolic energy source, underlies sustained reinforcement, and activates striatal circuitry. We found that mice with deletion of dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32) exclusively in D2R-expressing cells exhibited preferential D2R changes in the nucleus accumbens (NAc), a striatal region that critically regulates sucrose reinforcement. These changes coincided with perseverative and impulsive-like responding for sucrose pellets and sustained reinforcement learning of glucose-paired flavors. These mice were also characterized by significant glucose intolerance (ie, impaired glucose utilization). Systemic glucose administration significantly attenuated sucrose operant responding and D2R activation or blockade in the NAc bidirectionally modulated blood glucose levels and glucose tolerance. Collectively, these results implicate NAc D2R in regulating both peripheral glucose levels and glucose-dependent reinforcement learning behaviors and highlight the notion that glucose metabolic impairments arising from disrupted NAc D2R signaling are involved in compulsive and perseverative feeding behaviors.
Gomez, Juan L; Bonaventura, Jordi; Lesniak, Wojciech; Mathews, William B; Sysa-Shah, Polina; Rodriguez, Lionel A; Ellis, Randall J; Richie, Christopher T; Harvey, Brandon K; Dannals, Robert F; Pomper, Martin G; Bonci, Antonello; Michaelides, Michael
In: Science, 357 (6350), pp. 503–507, 2017, ISSN: 0036-8075.
Designer receptors exclusively activated by designer drugs (DREADDs) constitute a powerful chemogenetic strategy that can modulate nerve cell activity in freely moving animal preparations. Gomez et al. used radioligand receptor occupancy measurements and in vivo positron emission tomography to show that DREADDs expressed in the brain are not activated by the designer compound CNO (clozapine N-oxide). Instead, they are activated by the CNO metabolite clozapine, a drug with multiple endogenous targets. This may have important implications for the interpretation of results obtained with this popular technology.Science, this issue p. 503The chemogenetic technology DREADD (designer receptors exclusively activated by designer drugs) is widely used for remote manipulation of neuronal activity in freely moving animals. DREADD technology posits the use of textquotedblleftdesigner receptors,textquotedblright which are exclusively activated by the textquotedblleftdesigner drugtextquotedblright clozapine N-oxide (CNO). Nevertheless, the in vivo mechanism of action of CNO at DREADDs has never been confirmed. CNO does not enter the brain after systemic drug injections and shows low affinity for DREADDs. Clozapine, to which CNO rapidly converts in vivo, shows high DREADD affinity and potency. Upon systemic CNO injections, converted clozapine readily enters the brain and occupies central nervous system–expressed DREADDs, whereas systemic subthreshold clozapine injections induce preferential DREADD-mediated behaviors.
Michaelides, Michael; Hurd, Yasmin L
In: Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 40 (1), pp. 239–240, 2015, ISBN: 1740-634X; 0893-133X.
Michaelides, Michael; Anderson, Sarah Ann R; Ananth, Mala; Smirnov, Denis; Thanos, Panayotis K; Neumaier, John F; Wang, Gene-Jack; Volkow, Nora D; Hurd, Yasmin L
In: J Clin Invest, 123 (12), pp. 5342–5350, 2013, ISSN: 1558-8238 (Electronic); 0021-9738 (Linking).
The ability to map the functional connectivity of discrete cell types in the intact mammalian brain during behavior is crucial for advancing our understanding of brain function in normal and disease states. We combined designer receptor exclusively activated by designer drug (DREADD) technology and behavioral imaging with muPET and [18F]fluorodeoxyglucose (FDG) to generate whole-brain metabolic maps of cell-specific functional circuits during the awake, freely moving state. We have termed this approach DREADD-assisted metabolic mapping (DREAMM) and documented its ability in rats to map whole-brain functional anatomy. We applied this strategy to evaluating changes in the brain associated with inhibition of prodynorphin-expressing (Pdyn-expressing) and of proenkephalin-expressing (Penk-expressing) medium spiny neurons (MSNs) of the nucleus accumbens shell (NAcSh), which have been implicated in neuropsychiatric disorders. DREAMM revealed discrete behavioral manifestations and concurrent engagement of distinct corticolimbic networks associated with dysregulation of Pdyn and Penk in MSNs of the NAcSh. Furthermore, distinct neuronal networks were recruited in awake versus anesthetized conditions. These data demonstrate that DREAMM is a highly sensitive, molecular, high-resolution quantitative imaging approach.
Michaelides, Michael; Miller, Michael L; Subrize, Mike; Kim, Ronald; Robison, Lisa; Hurd, Yasmin L; Wang, Gene-Jack; Volkow, Nora D; Thanos, Panayotis K
In: Brain Res, 1512 , pp. 37–44, 2013, ISSN: 1872-6240 (Electronic); 0006-8993 (Linking).
Expectation of salient rewards and novelty seeking are processes implicated in substance use disorders but the neurobiological substrates underlying these associations are not well understood. To better understand the regional circuitry of novelty and reward preference, rats were conditioned to pair unique cues with bacon, an initially novel food, or chow, a familiar food. In the same animals, after training, cue-induced brain activity was measured, and the relationships between activity and preference for three rewards, the conditioned foods and ethanol (EtOH), were separately determined. Activity in response to the food paired cues was measured using brain glucose metabolism (BGluM). Rats favoring bacon-paired (BAP) cues had increased BGluM in mesocorticolimbic brain regions after exposure to these cues, while rats favoring chow-paired (CHP) cues showed relative deactivation in these regions. Rats exhibiting BAP cue-induced activation in prefrontal cortex (PFC) also consumed more EtOH while rats with cortical activation in response to CHP cues showed lower EtOH consumption. Additionally, long-term stable expression levels of PFC Grin2a, a subunit of the NMDA receptor, correlated with individual differences in EtOH preference insomuch that rats with high EtOH preference had enduringly low PFC Grin2a mRNA expression. No other glutamatergic, dopaminergic or endocannabinoid genes studied showed this relationship. Overall, these results suggest that natural variation in mesocorticolimbic sensitivity to reward-paired cues underlies behavioral preferences for and vulnerability to alcohol abuse, and support the notion of common neuronal circuits involved in food- and drug-seeking behavior. The findings also provide evidence that PFC NMDA-mediated glutamate signaling may modulate these associations.
Michaelides, Michael; Thanos, Panayotis K; Kim, Ronald; Cho, Jacob; Ananth, Mala; Wang, Gene-Jack; Volkow, Nora D
PET imaging predicts future body weight and cocaine preference. Journal Article
In: Neuroimage, 59 (2), pp. 1508–1513, 2012, ISSN: 1095-9572 (Electronic); 1053-8119 (Linking).
Deficits in dopamine D2/D3 receptor (D2R/D3R) binding availability using PET imaging have been reported in obese humans and rodents. Similar deficits have been reported in cocaine-addicts and cocaine-exposed primates. We found that D2R/D3R binding availability negatively correlated with measures of body weight at the time of scan (ventral striatum), at 1 (ventral striatum) and 2 months (dorsal and ventral striatum) post scan in rats. Cocaine preference was negatively correlated with D2R/D3R binding availability 2 months (ventral striatum) post scan. Our findings suggest that inherent deficits in striatal D2R/D3R signaling are related to obesity and drug addiction susceptibility and that ventral and dorsal striatum serve dissociable roles in maintaining weight gain and cocaine preference. Measuring D2R/D3R binding availability provides a way for assessing susceptibility to weight gain and cocaine abuse in rodents and given the translational nature of PET imaging, potentially primates and humans.
Michaelides, Michael; Thanos, Panayotis K; Volkow, Nora D; Wang, Gene-Jack
Translational Neuroimaging in Drug Addiction and Obesity Journal Article
In: ILAR Journal, 53 (1), pp. 59-68, 2012, ISSN: 1084-2020.
The use of translational noninvasive neuroimaging has revealed that drug addiction and obesity share striking similarities in functional impairment in discrete brain regions and neurotransmitter circuits. Imaging experiments in both humans and rodents (using complementary experimental designs) show similar abnormalities in brain glucose metabolism in the prefrontal cortex (involved in inhibitory control) and hippocampus (memory) as well as impairments in dopamine signaling in the striatum (involved in food and drug reward, goal orientation, motivation, and habit formation). In both species, many of these observations have been obtained through concurrent and parallel monitoring of both brain activity and behavioral manifestations during drug administration, food sensory (visual, olfactory) stimulation, and craving. This review aims to show that noninvasive brain imaging strategies such as small animal positron emission tomography offer significant potential and promise for modeling motivational disorders such as drug addiction and obesity in humans. Rodent addiction models will prove valuable for understanding brain responses to drug cues and will help guide treatment, especially in relapse situations triggered by exposure to conditioned drug cues.
Michaelides, Michael; Pascau, Javier; Gispert, Juan-Domingo; Delis, Foteini; Grandy, David K; Wang, Gene-Jack; Desco, Manuel; Rubinstein, Marcelo; Volkow, Nora D; Thanos, Panayotis K
In: Eur J Neurosci, 32 (4), pp. 668–676, 2010, ISSN: 1460-9568 (Electronic); 0953-816X (Linking).
Methylphenidate (MP) is widely used to treat attention deficit hyperactivity disorder (ADHD). Variable number of tandem repeats polymorphisms in the dopamine D4 receptor (D(4)) gene have been implicated in vulnerability to ADHD and the response to MP. Here we examined the contribution of dopamine D4 receptors (D4Rs) to baseline brain glucose metabolism and to the regional metabolic responses to MP. We compared brain glucose metabolism (measured with micro-positron emission tomography and [(18)F]2-fluoro-2-deoxy-D-glucose) at baseline and after MP (10 mg/kg, i.p.) administration in mice with genetic deletion of the D(4). Images were analyzed using a novel automated image registration procedure. Baseline D(4)(-/-) mice had lower metabolism in the prefrontal cortex (PFC) and greater metabolism in the cerebellar vermis (CBV) than D(4)(+/+) and D(4)(+/-) mice; when given MP, D(4)(-/-) mice increased metabolism in the PFC and decreased it in the CBV, whereas in D(4)(+/+) and D(4)(+/-) mice, MP decreased metabolism in the PFC and increased it in the CBV. These findings provide evidence that D4Rs modulate not only the PFC, which may reflect the activation by dopamine of D4Rs located in this region, but also the CBV, which may reflect an indirect modulation as D4Rs are minimally expressed in this region. As individuals with ADHD show structural and/or functional abnormalities in these brain regions, the association of ADHD with D4Rs may reflect its modulation of these brain regions. The differential response to MP as a function of genotype could explain differences in brain functional responses to MP between patients with ADHD and healthy controls and between patients with ADHD with different D(4) polymorphisms.