Our experiences come to shape our future behaviors and can having lasting effects on our quality of life. My research aims to understand how chronic exposure to particular stimuli (i.e. stress, food, drugs) alters the functioning of specific neural circuits. Following identification of the relevant circuits, I investigate the mechanisms that regulate these experience-dependent changes. This ultimately aids in our understanding of how maladaptive changes in brain function occur and how these changes result in psychiatric disorders.
My current focus is on specific neural circuits involved in reward processing and feeding behavior. I am discovering how various excitatory inputs to the nucleus accumbens, a critical brain node involved in processing the salience of events, modulate reward - related behaviors utilizing converging lines of inquiry. Specifically, I observe neuronal activity in awake behaving mice, and assess the mechanisms underlying changes in activity with electrophysiology. Finally, I then modulate specific circuits using optogenetics, a technique that provides spatio-temporal control over genetically identified cells, to determine the causal role of these circuits in reward-related behavior.


Honors & Awards

  • NARSAD YOUNG INVESTIGATOR AWARD, Brain and Behavior Research Foundation (2020-2021)

Education & Certifications

  • Doctor of Philosphy, Icahn School of Medicine at Mount Sinai, Neuroscience (2014)
  • BA, New York University, Psychology (2004)

All Publications

  • Input-specific modulation of murine nucleus accumbens differentially regulates hedonic feeding. Nature communications Christoffel, D. J., Walsh, J. J., Heifets, B. D., Hoerbelt, P., Neuner, S., Sun, G., Ravikumar, V. K., Wu, H., Halpern, C. H., Malenka, R. C. 2021; 12 (1): 2135


    Hedonic feeding is driven by the "pleasure" derived from consuming palatable food and occurs in the absence of metabolic need. It plays a critical role in the excessive feeding that underlies obesity. Compared to other pathological motivated behaviors, little is known about the neural circuit mechanisms mediating excessive hedonic feeding. Here, we show that modulation of prefrontal cortex (PFC) and anterior paraventricular thalamus (aPVT) excitatory inputs to the nucleus accumbens (NAc), a key node of reward circuitry, has opposing effects on high fat intake in mice. Prolonged high fat intake leads to input- and cell type-specific changes in synaptic strength. Modifying synaptic strength via plasticity protocols, either in an input-specific optogenetic or non-specific electrical manner, causes sustained changes in high fat intake. These results demonstrate that input-specific NAc circuit adaptations occur with repeated exposure to a potent natural reward and suggest that neuromodulatory interventions may be therapeutically useful for individuals with pathologic hedonic feeding.

    View details for DOI 10.1038/s41467-021-22430-7

    View details for PubMedID 33837200

  • Dissecting neural mechanisms of prosocial behaviors. Current opinion in neurobiology Walsh, J. J., Christoffel, D. J., Wu, X., Pomrenze, M. B., Malenka, R. C. 2020; 68: 9–14


    Prosocial behaviors are essential for group cooperation, which enrich life experience and enhance survival. These complex behaviors are governed by intricate interactions between numerous neural circuits functioning in concert. Impairments in prosocial interactions result from disruptions of this coordinated brain activity and are a prominent feature of several pathological conditions including autism spectrum disorder, depression and addiction. Here we highlight recent studies that use advanced techniques to anatomically map, monitor and manipulate neural circuits that influence prosocial behavior. These recent findings provide important clues to unravel the complexities of the neural mechanisms that mediate prosocial interactions and offer insights into new strategies for the treatment of aberrant social behavior.

    View details for DOI 10.1016/j.conb.2020.11.006

    View details for PubMedID 33278639

  • 5-HT release in nucleus accumbens rescues social deficits in mouse autism model NATURE Walsh, J. J., Christoffel, D. J., Heifets, B. D., Ben-Dor, G. A., Selimbeyoglu, A., Hung, L. W., Deisseroth, K., Malenka, R. C. 2018; 560 (7720): 589-+
  • Excitatory transmission at thalamo-striatal synapses mediates susceptibility to social stress. Nature neuroscience Christoffel, D. J., Golden, S. A., Walsh, J. J., Guise, K. G., Heshmati, M., Friedman, A. K., Dey, A., Smith, M., Rebusi, N., Pfau, M., Ables, J. L., Aleyasin, H., Khibnik, L. A., Hodes, G. E., Ben-Dor, G. A., Deisseroth, K., Shapiro, M. L., Malenka, R. C., Ibanez-Tallon, I., Han, M., Russo, S. J. 2015; 18 (7): 962-964


    Postsynaptic remodeling of glutamatergic synapses on ventral striatum (vSTR) medium spiny neurons (MSNs) is critical for shaping stress responses. However, it is unclear which presynaptic inputs are involved. Susceptible mice exhibited increased synaptic strength at intralaminar thalamus (ILT), but not prefrontal cortex (PFC), inputs to vSTR MSNs following chronic social stress. Modulation of ILT-vSTR versus PFC-vSTR neuronal activity differentially regulated dendritic spine plasticity and social avoidance.

    View details for DOI 10.1038/nn.4034

    View details for PubMedID 26030846

    View details for PubMedCentralID PMC4482771

  • Illuminating circuitry relevant to psychiatric disorders with optogenetics CURRENT OPINION IN NEUROBIOLOGY Steinberg, E. E., Christoffel, D. J., Deisseroth, K., Malenka, R. C. 2015; 30: 9-16


    The brain's remarkable capacity to generate cognition and behavior is mediated by an extraordinarily complex set of neural interactions that remain largely mysterious. This complexity poses a significant challenge in developing therapeutic interventions to ameliorate psychiatric disease. Accordingly, few new classes of drugs have been made available for patients with mental illness since the 1950s. Optogenetics offers the ability to selectively manipulate individual neural circuit elements that underlie disease-relevant behaviors and is currently accelerating the pace of preclinical research into neurobiological mechanisms of disease. In this review, we highlight recent findings from studies that employ optogenetic approaches to gain insight into normal and aberrant brain function relevant to mental illness. Emerging data from these efforts offers an exquisitely detailed picture of disease-relevant neural circuits in action, and hints at the potential of optogenetics to open up entirely new avenues in the treatment of psychiatric disorders.

    View details for DOI 10.1016/j.conb.2014.08.004

    View details for Web of Science ID 000348337600002

    View details for PubMedID 25215625

  • IkappaB kinase regulates social defeat stress induced synaptic and behavioral plasticity Journal of Neuroscience Christoffel, D. J., et al 2011; 32 (1): 314-21
  • 5-HT release in nucleus accumbens rescues social deficits in mouse autism model. Nature Walsh, J. J., Christoffel, D. J., Heifets, B. D., Ben-Dor, G. A., Selimbeyoglu, A., Hung, L. W., Deisseroth, K., Malenka, R. C. 2018


    Dysfunction in prosocial interactions is a core symptom of autism spectrum disorder. However, the neural mechanisms that underlie sociability are poorly understood, limiting the rational development of therapies to treat social deficits. Here we show in mice that bidirectional modulation of the release of serotonin (5-HT) from dorsal raphe neurons in the nucleus accumbens bidirectionally modifies sociability. In a mouse model of a common genetic cause of autism spectrum disorder-a copy number variation on chromosome 16p11.2-genetic deletion of the syntenic region from 5-HT neurons induces deficits in social behaviour and decreases dorsal raphe 5-HT neuronal activity. These sociability deficits can be rescued by optogenetic activation of dorsal raphe 5-HT neurons, an effect requiring and mimicked by activation of 5-HT1b receptors in the nucleus accumbens. These results demonstrate an unexpected role for 5-HT action in the nucleus accumbens in social behaviours, and suggest that targeting this mechanism may prove therapeutically beneficial.

    View details for PubMedID 30089910

  • Parallel circuits from the bed nuclei of stria terminalis to the lateral hypothalamus drive opposing emotional states NATURE NEUROSCIENCE Giardino, W. J., Eban-Rothschild, A., Christoffel, D. J., Li, S., Malenka, R. C., de Lecea, L. 2018; 21 (8): 1084-+
  • Cell-type-specific role for nucleus accumbens neuroligin-2 in depression and stress susceptibility. Proceedings of the National Academy of Sciences of the United States of America Heshmati, M. n., Aleyasin, H. n., Menard, C. n., Christoffel, D. J., Flanigan, M. E., Pfau, M. L., Hodes, G. E., Lepack, A. E., Bicks, L. K., Takahashi, A. n., Chandra, R. n., Turecki, G. n., Lobo, M. K., Maze, I. n., Golden, S. A., Russo, S. J. 2018; 115 (5): 1111–16


    Behavioral coping strategies are critical for active resilience to stress and depression; here we describe a role for neuroligin-2 (NLGN-2) in the nucleus accumbens (NAc). Neuroligins (NLGN) are a family of neuronal postsynaptic cell adhesion proteins that are constituents of the excitatory and inhibitory synapse. Importantly, NLGN-3 and NLGN-4 mutations are strongly implicated as candidates underlying the development of neuropsychiatric disorders with social disturbances such as autism, but the role of NLGN-2 in neuropsychiatric disease states is unclear. Here we show a reduction in NLGN-2 gene expression in the NAc of patients with major depressive disorder. Chronic social defeat stress in mice also decreases NLGN-2 selectively in dopamine D1-positive cells, but not dopamine D2-positive cells, within the NAc of stress-susceptible mice. Functional NLGN-2 knockdown produces bidirectional, cell-type-specific effects: knockdown in dopamine D1-positive cells promotes subordination and stress susceptibility, whereas knockdown in dopamine D2-positive cells mediates active defensive behavior. These findings establish a behavioral role for NAc NLGN-2 in stress and depression; provide a basis for targeted, cell-type specific therapy; and highlight the role of active behavioral coping mechanisms in stress susceptibility.

    View details for PubMedID 29339486

    View details for PubMedCentralID PMC5798379

  • Closing the loop on impulsivity via nucleus accumbens delta-band activity in mice and man. Proceedings of the National Academy of Sciences of the United States of America Wu, H. n., Miller, K. J., Blumenfeld, Z. n., Williams, N. R., Ravikumar, V. K., Lee, K. E., Kakusa, B. n., Sacchet, M. D., Wintermark, M. n., Christoffel, D. J., Rutt, B. K., Bronte-Stewart, H. n., Knutson, B. n., Malenka, R. C., Halpern, C. H. 2018; 115 (1): 192–97


    Reward hypersensitization is a common feature of neuropsychiatric disorders, manifesting as impulsivity for anticipated incentives. Temporally specific changes in activity within the nucleus accumbens (NAc), which occur during anticipatory periods preceding consummatory behavior, represent a critical opportunity for intervention. However, no available therapy is capable of automatically sensing and therapeutically responding to this vulnerable moment in time when anticipation-related neural signals may be present. To identify translatable biomarkers for an off-the-shelf responsive neurostimulation system, we record local field potentials from the NAc of mice and a human anticipating conventional rewards. We find increased power in 1- to 4-Hz oscillations predominate during reward anticipation, which can effectively trigger neurostimulation that reduces consummatory behavior in mice sensitized to highly palatable food. Similar oscillations are present in human NAc during reward anticipation, highlighting the translational potential of our findings in the development of a treatment for a major unmet need.

    View details for PubMedID 29255043

  • Susceptibility to chronic social stress increases plaque progression, vulnerability and platelet activation THROMBOSIS AND HAEMOSTASIS Giannarelli, C., Rodriguez, D. T., Zafar, M. U., Christoffel, D., Vialou, V., Pena, C., Badimon, A., Hodes, G. F., Mury, P., Rabkin, J., Alique, M., Villa, G., Argmann, C., Nestler, E. J., Russo, S. J., Badimon, J. J. 2017; 117 (4): 816-818

    View details for DOI 10.1160/TH16-10-0817

    View details for Web of Science ID 000398880400020

    View details for PubMedID 28078352

    View details for PubMedCentralID PMC5490439

  • Antipsychotic-induced Hdac2 transcription via NF-κB leads to synaptic and cognitive side effects. Nature neuroscience Ibi, D. n., de la Fuente Revenga, M. n., Kezunovic, N. n., Muguruza, C. n., Saunders, J. M., Gaitonde, S. A., Moreno, J. L., Ijaz, M. K., Santosh, V. n., Kozlenkov, A. n., Holloway, T. n., Seto, J. n., García-Bea, A. n., Kurita, M. n., Mosley, G. E., Jiang, Y. n., Christoffel, D. J., Callado, L. F., Russo, S. J., Dracheva, S. n., López-Giménez, J. F., Ge, Y. n., Escalante, C. R., Meana, J. J., Akbarian, S. n., Huntley, G. W., González-Maeso, J. n. 2017; 20 (9): 1247–59


    Antipsychotic drugs remain the standard for schizophrenia treatment. Despite their effectiveness in treating hallucinations and delusions, prolonged exposure to antipsychotic medications leads to cognitive deficits in both schizophrenia patients and animal models. The molecular mechanisms underlying these negative effects on cognition remain to be elucidated. Here we demonstrate that chronic antipsychotic drug exposure increases nuclear translocation of NF-κB in both mouse and human frontal cortex, a trafficking event triggered via 5-HT2A-receptor-dependent downregulation of the NF-κB repressor IκBα. This upregulation of NF-κB activity led to its increased binding at the Hdac2 promoter, thereby augmenting Hdac2 transcription. Deletion of HDAC2 in forebrain pyramidal neurons prevented the negative effects of antipsychotic treatment on synaptic remodeling and cognition. Conversely, virally mediated activation of NF-κB signaling decreased cortical synaptic plasticity via HDAC2. Together, these observations may aid in developing therapeutic strategies to improve the outcome of schizophrenia treatment.

    View details for DOI 10.1038/nn.4616

    View details for PubMedID 28783139

    View details for PubMedCentralID PMC5675106

  • Basal forebrain projections to the lateral habenula modulate aggression reward NATURE Golden, S. A., Heshmati, M., Flanigan, M., Christoffel, D. J., Guise, K., Pfau, M. L., Aleyasin, H., Menard, C., Zhang, H., Hodes, G. E., Bregman, D., Khibnik, L., Tai, J., Rebusi, N., Krawitz, B., Chaudhury, D., Walsh, J. J., Han, M., Shapiro, M. L., Russo, S. J. 2016; 534 (7609): 688-?


    Maladaptive aggressive behaviour is associated with a number of neuropsychiatric disorders and is thought to result partly from the inappropriate activation of brain reward systems in response to aggressive or violent social stimuli. Nuclei within the ventromedial hypothalamus, extended amygdala and limbic circuits are known to encode initiation of aggression; however, little is known about the neural mechanisms that directly modulate the motivational component of aggressive behaviour. Here we established a mouse model to measure the valence of aggressive inter-male social interaction with a smaller subordinate intruder as reinforcement for the development of conditioned place preference (CPP). Aggressors develop a CPP, whereas non-aggressors develop a conditioned place aversion to the intruder-paired context. Furthermore, we identify a functional GABAergic projection from the basal forebrain (BF) to the lateral habenula (lHb) that bi-directionally controls the valence of aggressive interactions. Circuit-specific silencing of GABAergic BF-lHb terminals of aggressors with halorhodopsin (NpHR3.0) increases lHb neuronal firing and abolishes CPP to the intruder-paired context. Activation of GABAergic BF-lHb terminals of non-aggressors with channelrhodopsin (ChR2) decreases lHb neuronal firing and promotes CPP to the intruder-paired context. Finally, we show that altering inhibitory transmission at BF-lHb terminals does not control the initiation of aggressive behaviour. These results demonstrate that the BF-lHb circuit has a critical role in regulating the valence of inter-male aggressive behaviour and provide novel mechanistic insight into the neural circuits modulating aggression reward processing.

    View details for DOI 10.1038/nature18601

    View details for Web of Science ID 000378676000037

    View details for PubMedID 27357796

    View details for PubMedCentralID PMC4930107

  • Genetic and Stress-Induced Loss of NG2 Glia Triggers Emergence of Depressive-like Behaviors through Reduced Secretion of FGF2. Neuron Birey, F. n., Kloc, M. n., Chavali, M. n., Hussein, I. n., Wilson, M. n., Christoffel, D. J., Chen, T. n., Frohman, M. A., Robinson, J. K., Russo, S. J., Maffei, A. n., Aguirre, A. n. 2015


    NG2-expressing glia (NG2 glia) are a uniformly distributed and mitotically active pool of cells in the central nervous system (CNS). In addition to serving as progenitors of myelinating oligodendrocytes, NG2 glia might also fulfill physiological roles in CNS homeostasis, although the mechanistic nature of such roles remains unclear. Here, we report that ablation of NG2 glia in the prefrontal cortex (PFC) of the adult brain causes deficits in excitatory glutamatergic neurotransmission and astrocytic extracellular glutamate uptake and induces depressive-like behaviors in mice. We show in parallel that chronic social stress causes NG2 glia density to decrease in areas critical to Major Depressive Disorder (MDD) pathophysiology at the time of symptom emergence in stress-susceptible mice. Finally, we demonstrate that loss of NG2 glial secretion of fibroblast growth factor 2 (FGF2) suffices to induce the same behavioral deficits. Our findings outline a pathway and role for NG2 glia in CNS homeostasis and mood disorders.

    View details for PubMedID 26606998

  • Stress and CRF gate neural activation of BDNF in the mesolimbic reward pathway NATURE NEUROSCIENCE Walsh, J. J., Friedman, A. K., Sun, H., Heller, E. A., Ku, S. M., Juarez, B., Burnham, V. L., Mazei-Robison, M. S., Ferguson, D., Golden, S. A., Koo, J. W., Chaudhury, D., Christoffe, D. J., Pomeranz, L., Friedman, J. M., Russo, S. J., Nestler, E. J., Han, M. 2014; 17 (1): 27-29


    Mechanisms controlling release of brain-derived neurotrophic factor (BDNF) in the mesolimbic dopamine reward pathway remain unknown. We report that phasic optogenetic activation of this pathway increases BDNF amounts in the nucleus accumbens (NAc) of socially stressed mice but not of stress-naive mice. This stress gating of BDNF signaling is mediated by corticotrophin-releasing factor (CRF) acting in the NAc. These results unravel a stress context-detecting function of the brain's mesolimbic circuit.

    View details for DOI 10.1038/nn.3591

    View details for Web of Science ID 000329080000009

    View details for PubMedID 24270188

    View details for PubMedCentralID PMC3984932

  • Individual differences in the peripheral immune system promote resilience versus susceptibility to social stress. Proceedings of the National Academy of Sciences of the United States of America Hodes, G. E., Pfau, M. L., Leboeuf, M. n., Golden, S. A., Christoffel, D. J., Bregman, D. n., Rebusi, N. n., Heshmati, M. n., Aleyasin, H. n., Warren, B. L., Lebonté, B. n., Horn, S. n., Lapidus, K. A., Stelzhammer, V. n., Wong, E. H., Bahn, S. n., Krishnan, V. n., Bolaños-Guzman, C. A., Murrough, J. W., Merad, M. n., Russo, S. J. 2014; 111 (45): 16136–41


    Depression and anxiety disorders are associated with increased release of peripheral cytokines; however, their functional relevance remains unknown. Using a social stress model in mice, we find preexisting individual differences in the sensitivity of the peripheral immune system that predict and promote vulnerability to social stress. Cytokine profiles were obtained 20 min after the first social stress exposure. Of the cytokines regulated by stress, IL-6 was most highly up-regulated only in mice that ultimately developed a susceptible behavioral phenotype following a subsequent chronic stress, and levels remained elevated for at least 1 mo. We confirmed a similar elevation of serum IL-6 in two separate cohorts of patients with treatment-resistant major depressive disorder. Before any physical contact in mice, we observed individual differences in IL-6 levels from ex vivo stimulated leukocytes that predict susceptibility versus resilience to a subsequent stressor. To shift the sensitivity of the peripheral immune system to a pro- or antidepressant state, bone marrow (BM) chimeras were generated by transplanting hematopoietic progenitor cells from stress-susceptible mice releasing high IL-6 or from IL-6 knockout (IL-6(-/-)) mice. Stress-susceptible BM chimeras exhibited increased social avoidance behavior after exposure to either subthreshold repeated social defeat stress (RSDS) or a purely emotional stressor termed witness defeat. IL-6(-/-) BM chimeric and IL-6(-/-) mice, as well as those treated with a systemic IL-6 monoclonal antibody, were resilient to social stress. These data establish that preexisting differences in stress-responsive IL-6 release from BM-derived leukocytes functionally contribute to social stress-induced behavioral abnormalities.

    View details for DOI 10.1073/pnas.1415191111

    View details for PubMedID 25331895

  • Kalirin-7 Mediates Cocaine-Induced AMPA Receptor and Spine Plasticity, Enabling Incentive Sensitization JOURNAL OF NEUROSCIENCE Wang, X., Cahill, M. E., Werner, C. T., Christoffel, D. J., Golden, S. A., Xie, Z., Loweth, J. A., Marinelli, M., Russo, S. J., Penzes, P., Wolf, M. E. 2013; 33 (27): 11012-U410


    It is well established that behavioral sensitization to cocaine is accompanied by increased spine density and AMPA receptor (AMPAR) transmission in the nucleus accumbens (NAc), but two major questions remain unanswered. Are these adaptations mechanistically coupled? And, given that they can be dissociated from locomotor sensitization, what is their functional significance? We tested the hypothesis that the guanine-nucleotide exchange factor Kalirin-7 (Kal-7) couples cocaine-induced AMPAR and spine upregulation and that these adaptations underlie sensitization of cocaine's incentive-motivational properties-the properties that make it "wanted." Rats received eight daily injections of saline or cocaine. On withdrawal day 14, we found that Kal-7 levels and activation of its downstream effectors Rac-1 and PAK were increased in the NAc of cocaine-sensitized rats. Furthermore, AMPAR surface expression and spine density were increased, as expected. To determine whether these changes require Kal-7, a lentiviral vector expressing Kal-7 shRNA was injected into the NAc core before cocaine exposure. Knocking down Kal-7 abolished the AMPAR and spine upregulation normally seen during cocaine withdrawal. Despite the absence of these adaptations, rats with reduced Kal-7 levels developed locomotor sensitization. However, incentive sensitization, which was assessed by how rapidly rats learned to self-administer a threshold dose of cocaine, was severely impaired. These results identify a signaling pathway coordinating AMPAR and spine upregulation during cocaine withdrawal, demonstrate that locomotor and incentive sensitization involve divergent mechanisms, and link enhanced excitatory transmission in the NAc to incentive sensitization.

    View details for DOI 10.1523/JNEUROSCI.1097-13.2013

    View details for Web of Science ID 000321258000008

    View details for PubMedID 23825406

  • Epigenetic regulation of RAC1 induces synaptic remodeling in stress disorders and depression NATURE MEDICINE Golden, S. A., Christoffel, D. J., Heshmati, M., Hodes, G. E., Magida, J., Davis, K., Cahill, M. E., Dias, C., Ribeiro, E., Ables, J. L., Kennedy, P. J., Robison, A. J., Gonzalez-Maeso, J., Neve, R. L., Turecki, G., Ghose, S., Tamminga, C. A., Russo, S. J. 2013; 19 (3): 337-344


    Depression induces structural and functional synaptic plasticity in brain reward circuits, although the mechanisms promoting these changes and their relevance to behavioral outcomes are unknown. Transcriptional profiling of the nucleus accumbens (NAc) for Rho GTPase-related genes, which are known regulators of synaptic structure, revealed a sustained reduction in RAS-related C3 botulinum toxin substrate 1 (Rac1) expression after chronic social defeat stress. This was associated with a repressive chromatin state surrounding the proximal promoter of Rac1. Inhibition of class 1 histone deacetylases (HDACs) with MS-275 rescued both the decrease in Rac1 transcription after social defeat stress and depression-related behavior, such as social avoidance. We found a similar repressive chromatin state surrounding the RAC1 promoter in the NAc of subjects with depression, which corresponded with reduced RAC1 transcription. Viral-mediated reduction of Rac1 expression or inhibition of Rac1 activity in the NAc increases social defeat-induced social avoidance and anhedonia in mice. Chronic social defeat stress induces the formation of stubby excitatory spines through a Rac1-dependent mechanism involving the redistribution of synaptic cofilin, an actin-severing protein downstream of Rac1. Overexpression of constitutively active Rac1 in the NAc of mice after chronic social defeat stress reverses depression-related behaviors and prunes stubby spines. Taken together, our data identify epigenetic regulation of RAC1 in the NAc as a disease mechanism in depression and reveal a functional role for Rac1 in rodents in regulating stress-related behaviors.

    View details for DOI 10.1038/nm.3090

    View details for Web of Science ID 000316040700027

    View details for PubMedID 23416703

  • Rapid regulation of depression-related behaviours by control of midbrain dopamine neurons NATURE Chaudhury, D., Walsh, J. J., Friedman, A. K., Juarez, B., Ku, S. M., Koo, J. W., Ferguson, D., Tsai, H., Pomeranz, L., Christoffel, D. J., Nectow, A. R., Ekstrand, M., Domingos, A., Mazei-Robison, M. S., Mouzon, E., Lobo, M. K., Neve, R. L., Friedman, J. M., Russo, S. J., Deisseroth, K., Nestler, E. J., Han, M. 2013; 493 (7433): 532-?


    Ventral tegmental area (VTA) dopamine neurons in the brain's reward circuit have a crucial role in mediating stress responses, including determining susceptibility versus resilience to social-stress-induced behavioural abnormalities. VTA dopamine neurons show two in vivo patterns of firing: low frequency tonic firing and high frequency phasic firing. Phasic firing of the neurons, which is well known to encode reward signals, is upregulated by repeated social-defeat stress, a highly validated mouse model of depression. Surprisingly, this pathophysiological effect is seen in susceptible mice only, with no apparent change in firing rate in resilient individuals. However, direct evidence--in real time--linking dopamine neuron phasic firing in promoting the susceptible (depression-like) phenotype is lacking. Here we took advantage of the temporal precision and cell-type and projection-pathway specificity of optogenetics to show that enhanced phasic firing of these neurons mediates susceptibility to social-defeat stress in freely behaving mice. We show that optogenetic induction of phasic, but not tonic, firing in VTA dopamine neurons of mice undergoing a subthreshold social-defeat paradigm rapidly induced a susceptible phenotype as measured by social avoidance and decreased sucrose preference. Optogenetic phasic stimulation of these neurons also quickly induced a susceptible phenotype in previously resilient mice that had been subjected to repeated social-defeat stress. Furthermore, we show differences in projection-pathway specificity in promoting stress susceptibility: phasic activation of VTA neurons projecting to the nucleus accumbens (NAc), but not to the medial prefrontal cortex (mPFC), induced susceptibility to social-defeat stress. Conversely, optogenetic inhibition of the VTA-NAc projection induced resilience, whereas inhibition of the VTA-mPFC projection promoted susceptibility. Overall, these studies reveal novel firing-pattern- and neural-circuit-specific mechanisms of depression.

    View details for DOI 10.1038/nature11713

    View details for Web of Science ID 000313871400038

    View details for PubMedID 23235832

    View details for PubMedCentralID PMC3554860

  • IkappaB kinase regulates social defeat stress induced synaptic and behavioral plasticity Neuropsychopharmacology Christoffel, D. J., et al 2012; 37 (12): 2615-23
  • Effects of inhibitor of κB kinase activity in the nucleus accumbens on emotional behavior. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology Christoffel, D. J., Golden, S. A., Heshmati, M. n., Graham, A. n., Birnbaum, S. n., Neve, R. L., Hodes, G. E., Russo, S. J. 2012; 37 (12): 2615–23


    Inhibitor of κB kinase (IκK) has historically been studied in the context of immune response and inflammation, but recent evidence demonstrates that IκK activity is necessary and sufficient for regulation of neuronal function. Chronic social defeat stress of mice increases IκK activity in the nucleus accumbens (NAc) and this increase is strongly correlated to depression-like behaviors. Inhibition of IκK signaling results in a reversal of chronic social defeat stress-induced social avoidance behavior. Here, we more completely define the role of IκK in anxiety and depressive-like behaviors. Mice underwent stereotaxic microinjection of a herpes simplex virus expressing either green fluorescent protein, a constitutively active form of IκK (IκKca), or a dominant negative form of IκK into the NAc. Of all three experimental groups, only mice expressing IκKca show a behavioral phenotype. Expression of IκKca results in a decrease in the time spent in the non-periphery zones of an open field arena and increased time spent immobile during a forced swim test. No baseline differences in sucrose preference were observed, but following the acute swim stress we noted a marked reduction in sucrose preference. To determine whether IκK activity alters responses to other acute stressors, we examined behavior and spine morphology in mice undergoing an acute social defeat stress. We found that IκKca enhanced social avoidance behavior and promoted thin spine formation. These data show that IκK in NAc is a critical regulator of both depressive- and anxiety-like states and may do so by promoting the formation of immature excitatory synapses.

    View details for PubMedID 22781845

    View details for PubMedCentralID PMC3473326

  • Rac1 is essential in cocaine-induced structural plasticity of nucleus accumbens neurons. Nature neuroscience Dietz, D. M., Sun, H. n., Lobo, M. K., Cahill, M. E., Chadwick, B. n., Gao, V. n., Koo, J. W., Mazei-Robison, M. S., Dias, C. n., Maze, I. n., Damez-Werno, D. n., Dietz, K. C., Scobie, K. N., Ferguson, D. n., Christoffel, D. n., Ohnishi, Y. n., Hodes, G. E., Zheng, Y. n., Neve, R. L., Hahn, K. M., Russo, S. J., Nestler, E. J. 2012; 15 (6): 891–96


    Repeated cocaine administration increases the dendritic arborization of nucleus accumbens neurons, but the underlying signaling events remain unknown. Here we show that repeated exposure to cocaine negatively regulates the active form of Rac1, a small GTPase that controls actin remodeling in other systems. Further, we show, using viral-mediated gene transfer, that overexpression of a dominant negative mutant of Rac1 or local knockout of Rac1 is sufficient to increase the density of immature dendritic spines on nucleus accumbens neurons, whereas overexpression of a constitutively active Rac1 or light activation of a photoactivatable form of Rac1 blocks the ability of repeated cocaine exposure to produce this effect. Downregulation of Rac1 activity likewise promotes behavioral responses to cocaine exposure, with activation of Rac1 producing the opposite effect. These findings establish that Rac1 signaling mediates structural and behavioral plasticity in response to cocaine exposure.

    View details for PubMedID 22522400

    View details for PubMedCentralID PMC3565539

  • Structural and synaptic plasticity in stress-related disorders. Reviews in the neurosciences Christoffel, D. J., Golden, S. A., Russo, S. J. 2011; 22 (5): 535–49


    Abstract Stress can have a lasting impact on the structure and function of brain circuitry that results in long-lasting changes in the behavior of an organism. Synaptic plasticity is the mechanism by which information is stored and maintained within individual synapses, neurons, and neuronal circuits to guide the behavior of an organism. Although these mechanisms allow the organism to adapt to its constantly evolving environment, not all of these adaptations are beneficial. Under prolonged bouts of physical or psychological stress, these mechanisms become dysregulated, and the connectivity between brain regions becomes unbalanced, resulting in pathological behaviors. In this review, we highlight the effects of stress on the structure and function of neurons within the mesocorticolimbic brain systems known to regulate mood and motivation. We then discuss the implications of these spine adaptations on neuronal activity and pathological behaviors implicated in mood disorders. Finally, we end by discussing recent brain imaging studies in human depression within the context of these basic findings to provide insight into the underlying mechanisms leading to neural dysfunction in depression.

    View details for PubMedID 21967517

    View details for PubMedCentralID PMC3212803

  • IκB kinase regulates social defeat stress-induced synaptic and behavioral plasticity. The Journal of neuroscience : the official journal of the Society for Neuroscience Christoffel, D. J., Golden, S. A., Dumitriu, D. n., Robison, A. J., Janssen, W. G., Ahn, H. F., Krishnan, V. n., Reyes, C. M., Han, M. H., Ables, J. L., Eisch, A. J., Dietz, D. M., Ferguson, D. n., Neve, R. L., Greengard, P. n., Kim, Y. n., Morrison, J. H., Russo, S. J. 2011; 31 (1): 314–21


    The neurobiological underpinnings of mood and anxiety disorders have been linked to the nucleus accumbens (NAc), a region important in processing the rewarding and emotional salience of stimuli. Using chronic social defeat stress, an animal model of mood and anxiety disorders, we investigated whether alterations in synaptic plasticity are responsible for the long-lasting behavioral symptoms induced by this form of stress. We hypothesized that chronic social defeat stress alters synaptic strength or connectivity of medium spiny neurons (MSNs) in the NAc to induce social avoidance. To test this, we analyzed the synaptic profile of MSNs via confocal imaging of Lucifer-yellow-filled cells, ultrastructural analysis of the postsynaptic density, and electrophysiological recordings of miniature EPSCs (mEPSCs) in mice after social defeat. We found that NAc MSNs have more stubby spine structures with smaller postsynaptic densities and an increase in the frequency of mEPSCs after social defeat. In parallel to these structural changes, we observed significant increases in IκB kinase (IKK) in the NAc after social defeat, a molecular pathway that has been shown to regulate neuronal morphology. Indeed, we find using viral-mediated gene transfer of dominant-negative and constitutively active IKK mutants that activation of IKK signaling pathways during social defeat is both necessary and sufficient to induce synaptic alterations and behavioral effects of the stress. These studies establish a causal role for IKK in regulating stress-induced adaptive plasticity and may present a novel target for drug development in the treatment of mood and anxiety disorders in humans.

    View details for PubMedID 21209217

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  • Stereologic estimates of total spinophilin-immunoreactive spine number in area 9 and the CA1 field: relationship with the progression of Alzheimer's disease. Neurobiology of aging Akram, A. n., Christoffel, D. n., Rocher, A. B., Bouras, C. n., Kövari, E. n., Perl, D. P., Morrison, J. H., Herrmann, F. R., Haroutunian, V. n., Giannakopoulos, P. n., Hof, P. R. 2008; 29 (9): 1296–1307


    The loss of presynaptic markers is thought to represent a strong pathologic correlate of cognitive decline in Alzheimer's disease (AD). Spinophilin is a postsynaptic marker mainly located to the heads of dendritic spines. We assessed total numbers of spinophilin-immunoreactive puncta in the CA1 and CA3 fields of hippocampus and area 9 in 18 elderly individuals with various degrees of cognitive decline. The decrease in spinophilin-immunoreactivity was significantly related to both Braak neurofibrillary tangle (NFT) staging and clinical severity but not A beta deposition staging. The total number of spinophilin-immunoreactive puncta in CA1 field and area 9 were significantly related to MMSE scores and predicted 23.5 and 61.9% of its variability. The relationship between total number of spinophilin-immunoreactive puncta in CA1 field and MMSE scores did not persist when adjusting for Braak NFT staging. In contrast, the total number of spinophilin-immunoreactive puncta in area 9 was still significantly related to the cognitive outcome explaining an extra 9.6% of MMSE and 25.6% of the Clinical Dementia Rating scores variability. Our data suggest that neocortical dendritic spine loss is an independent parameter to consider in AD clinicopathologic correlations.

    View details for PubMedID 17420070

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  • Pepsin pretreatment allows collagen IV immunostaining of blood vessels in adult mouse brain. Journal of neuroscience methods Franciosi, S. n., De Gasperi, R. n., Dickstein, D. L., English, D. F., Rocher, A. B., Janssen, W. G., Christoffel, D. n., Sosa, M. A., Hof, P. R., Buxbaum, J. D., Elder, G. A. 2007; 163 (1): 76–82


    While the brain vasculature can be imaged with many methods, immunohistochemistry has distinct advantages due to its simplicity and applicability to archival tissue. However, immunohistochemical staining of the murine brain vasculature in aldehyde fixed tissue has proven elusive and inconsistent using current protocols. Here we investigated whether antigen retrieval methods could improve vascular staining in the adult mouse brain. We found that pepsin digestion prior to immunostaining unmasked widespread collagen IV staining of the cerebrovasculature in the adult mouse brain. Pepsin treatment also unmasked widespread vascular staining with laminin, but only marginally improved isolectin B4 staining and did not enhance vascular staining with fibronectin, perlecan or CD146. Collagen IV immunoperoxidase staining was easily combined with cresyl violet counterstaining making it suitable for stereological analyses of both vascular and neuronal parameters in the same tissue section. This method should be widely applicable for labeling the brain vasculature of the mouse in aldehyde fixed tissue from both normal and pathological states.

    View details for PubMedID 17403541

    View details for PubMedCentralID PMC1931483