This proposal continues our characterization of the role of neurotrophic signaling pathways in the neural plasticity induced in the ventral tegmental area (VTA)-nucleus accumbens (NAc) reward circuit by chronic exposure to opiate or stimulant drugs of abuse. The proposal has three Aims: 1) to delineate the cell-type specific actions of BDNF-TrkB signaling in the VTA-NAc in regulating molecular, cellular, and behavioral responses to opiates and cocaine;2) to delineate the adaptations in BDNF-TrkB signaling cascades that mediate the ability of opiates to induce morphological changes in VTA dopamine neurons;and 3) to delineate the adaptations in BDNF-TrkB signaling cascades that mediate the ability of cocaine and opiates to induce opposite morphological changes in NAc medium spiny neurons. We have made important progress in each of these Aims over the past 5 years, and have substantial preliminary data to support highly penetrating and mechanistic studies over the proposed new grant period. Using genetic mutant mice and viral-mediated gene transfer, which has enabled highly localized knockouts of BDNF or TrkB within the VTA or NAc of adult animals, we have demonstrated distinct roles for BDNF-TrkB signaling in regulating responses to opiates and cocaine. Using more advanced tools, which now enable such knockouts in specific neuronal cell types within these brain regions, we will characterize the specific influence of D1 vs. D2 containing NAc medium spiny neurons, and VTA dopamine neurons, in these phenomena. One of the most dramatic changes that opiates induce in VTA dopamine neurons is a decrease in their overall size. This decrease is mediated by an impairment in BDNF signaling within these neurons, specifically, downregulation of the IRS-AKT pathway. We now have evidence that this downregulation is part of overall opiate-induced adaptations in AKT-RHEB-mTOR signaling. The proposed experiments are designed to further establish the detailed molecular events that underlie this morphological adaptation. In contrast, cocaine and opiates induce distinct changes in NAc medium spiny neurons: cocaine increases, whereas opiates decrease, the neurons'dendritic arborizations and spine density. We have shown that these adaptations too involve altered BDNF signaling, and now propose to further characterize the precise changes in neurotrophic signaling pathways, including changes in NF?B signaling that mediate these adaptations. Together, the proposed experiments will provide fundamentally new insight into the dramatic ways in which opiates and stimulants change VTA-NAc neurons, information which could be mined in future years to define improved diagnostic tests and treatments for drug addiction.

Public Health Relevance

The objective of this grant is to study the role of neurotrophic signaling pathways, acting in the brain's reward circuits, in drug abuse models in mice. We investigate the influence of chronic exposure to drugs of abuse on levels and activity of these complex signaling pathways within brain reward regions. We then manipulate the activity of specific signaling proteins in reward regions by use of genetic mutant mice or viral mediated gene transfer, and study the molecular, cellular, and behavioral consequences of these manipulations. Together, these studies promise to provide fundamentally novel information concerning how drugs of abuse alter the brain's reward circuits after chronic administration, and to offer new leads toward the development of improved diagnostic tests and more effective treatments of drug addiction.

National Institute of Health (NIH)
National Institute on Drug Abuse (NIDA)
Research Project (R01)
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Study Section
Molecular Neuropharmacology and Signaling Study Section (MNPS)
Program Officer
Pilotte, Nancy S
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Icahn School of Medicine at Mount Sinai
Schools of Medicine
New York
United States
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Heller, Elizabeth A; Kaska, Sophia; Fallon, Barbara et al. (2015) Morphine and cocaine increase serum- and glucocorticoid-inducible kinase 1 activity in the ventral tegmental area. J Neurochem 132:243-53
Mazei-Robison, Michelle S; Appasani, Raghu; Edwards, Scott et al. (2014) Self-administration of ethanol, cocaine, or nicotine does not decrease the soma size of ventral tegmental area dopamine neurons. PLoS One 9:e95962
Walsh, Jessica J; Friedman, Allyson K; Sun, Haosheng et al. (2014) Stress and CRF gate neural activation of BDNF in the mesolimbic reward pathway. Nat Neurosci 17:27-9
Dong, Yan; Nestler, Eric J (2014) The neural rejuvenation hypothesis of cocaine addiction. Trends Pharmacol Sci 35:374-83
Scobie, Kimberly N; Damez-Werno, Diane; Sun, HaoSheng et al. (2014) Essential role of poly(ADP-ribosyl)ation in cocaine action. Proc Natl Acad Sci U S A 111:2005-10
Koo, Ja Wook; Lobo, Mary Kay; Chaudhury, Dipesh et al. (2014) Loss of BDNF signaling in D1R-expressing NAc neurons enhances morphine reward by reducing GABA inhibition. Neuropsychopharmacology 39:2646-53
Lee, Brian R; Ma, Yao-Ying; Huang, Yanhua H et al. (2013) Maturation of silent synapses in amygdala-accumbens projection contributes to incubation of cocaine craving. Nat Neurosci 16:1644-51
Dietz, David M; Sun, Haosheng; Lobo, Mary Kay et al. (2012) Rac1 is essential in cocaine-induced structural plasticity of nucleus accumbens neurons. Nat Neurosci 15:891-6
Mazei-Robison, Michelle S; Koo, Ja Wook; Friedman, Allyson K et al. (2011) Role for mTOR signaling and neuronal activity in morphine-induced adaptations in ventral tegmental area dopamine neurons. Neuron 72:977-90
LaPlant, Quincey; Vialou, Vincent; Covington 3rd, Herbert E et al. (2010) Dnmt3a regulates emotional behavior and spine plasticity in the nucleus accumbens. Nat Neurosci 13:1137-43

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