To date, there are no effective therapeutic treatments for cocaine craving and relapse, which can be precipitated in abstinent human addicts by re-exposure to environmental stimuli that were previously associated with drug taking. This cue-induced drug craving in humans progressively increases during early drug withdrawal and remains high throughout extended periods of drug abstinence. This phenomenon was modeled in rats using a self-administration/reinstatement paradigm in which responsiveness to cues previously paired with cocaine was shown to progressively increase (or """"""""incubate"""""""") over the first two months of forced drug abstinence. Brain-derived neurotrophic factor (BDNF) protein expression also was increased in mesocorticolimbic nuclei according to a similar time course as the incubation of cocaine craving (ICC), which suggests that BDNF may potentiate the ongoing expression of ICC. However, the precise molecular mechanisms that regulate time-dependent changes in BDNF expression during ICC remain to be determined. Preliminary data from our lab indicate for the first time that mesolimbic BDNF mRNA expression also is increased during cocaine abstinence according to a similar time course to the expression of ICC. The goal of the proposed Research and Training Plans is to acquire molecular neuroscience techniques through supervised hands-on training and didactic coursework in order to incorporate molecular/epigenetic methods into Specific Aims focused on elucidating the mechanisms that regulate BDNF expression during ICC. The main hypothesis of this K01 application is that altered BDNF mRNA expression during ICC is mediated by chromatin remodeling within BDNF promoters.
Aim 1 will require training in Western blot, ELISA, and real-time PCR methods in order to determine the precise time course that BDNF mRNA and protein expression is regulated within mesocorticolimbic nuclei during the development and expression of ICC.
Aim 2 will require proficiency in ChIP techniques in order to examine chromatin remodeling (i.e. histone acetylation and/or methylation) at BDNF promoters associated with increased BDNF mRNA expression during ICC. In order to identify the enzymes that regulate chromatin structure at BDNF promoters, ChIP methods also will be used in Aim 2 to isolate transcription factors [TFs] bound to BDNF promoters. Further training in molecular biology, will be required in Aim 3 in order to use viral-mediated delivery of siRNAs to knock-down TFs that bind to BDNF promoters during ICC. Expression of ICC as well as altered histone acetylation and/or methylation will be examined following viral-mediated TF knock-down in order to demonstrate a causal association between DNA- protein interactions, chromatin remodeling, enhanced BDNF expression and ICC. Understanding how chromatin remodeling alters BDNF expression during ICC will contribute important insights into the emerging field of epigenetic addiction research and may provide novel drug targets aimed at reducing cocaine craving and relapse in human addicts.
These proposed experiments will investigate the molecular mechanisms (i.e., epigenetic/chromatin remodeling) that regulate mesolimbic brain-derived neurotrophic factor (BDNF) expression during the incubation of cocaine craving, an animal model of drug craving and relapse in human addicts. This proposal aims to identify the molecular substrates that regulate chromatin structure and transcription of BDNF promoter regions during the incubation of cocaine craving. Therefore, this proposal will provide insight into the epigenetic mechanisms underlying cocaine addiction as well as identify novel targets for treating drug craving and relapse.
|Maurer, John J; Sandager-Nielsen, Karin; Schmidt, Heath D (2017) Attenuation of nicotine taking and seeking in rats by the stoichiometry-selective alpha4beta2 nicotinic acetylcholine receptor positive allosteric modulator NS9283. Psychopharmacology (Berl) 234:475-484|
|Wimmer, M E; Briand, L A; Fant, B et al. (2017) Paternal cocaine taking elicits epigenetic remodeling and memory deficits in male progeny. Mol Psychiatry 22:1641-1650|
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|White, Samantha L; Vassoler, Fair M; Schmidt, Heath D et al. (2016) Enhanced anxiety in the male offspring of sires that self-administered cocaine. Addict Biol 21:802-810|
|Ortinski, Pavel I; Briand, Lisa A; Pierce, R Christopher et al. (2015) Cocaine-seeking is associated with PKC-dependent reduction of excitatory signaling in accumbens shell D2 dopamine receptor-expressing neurons. Neuropharmacology 92:80-9|
|Guercio, Leonardo A; Schmidt, Heath D; Pierce, R Christopher (2015) Deep brain stimulation of the nucleus accumbens shell attenuates cue-induced reinstatement of both cocaine and sucrose seeking in rats. Behav Brain Res 281:125-30|
|Schmidt, H D; McFarland, K N; Darnell, S B et al. (2015) ADAR2-dependent GluA2 editing regulates cocaine seeking. Mol Psychiatry 20:1460-6|
|Schmidt, Heath D; Kimmey, Blake A; Arreola, Adrian C et al. (2015) Group I metabotropic glutamate receptor-mediated activation of PKC gamma in the nucleus accumbens core promotes the reinstatement of cocaine seeking. Addict Biol 20:285-96|
|Rasakham, Khampaseuth; Schmidt, Heath D; Kay, Kevin et al. (2014) Synapse density and dendritic complexity are reduced in the prefrontal cortex following seven days of forced abstinence from cocaine self-administration. PLoS One 9:e102524|
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