Transcriptional profiling reveals differential changes in the expression of oxytocin and CARTpt mRNAs in the nucleus accumbens and dorsal striatum of rats (striatum)
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ABSTRACT: Methamphetamine addiction is mimicked in rats that self-administer the drug and accelerate their intake when given long access to it. Self-administration (SA) models do not include adverse consequences that are necessary to reach a diagnosis of addiction in humans. Here, we studied transcriptional consequences of methamphetamine SA and repeated foot-shocks in rat brain.
Project description:Methamphetamine addiction is mimicked in rats that self-administer the drug and accelerate their intake when given long access to it. Self-administration (SA) models do not include adverse consequences that are necessary to reach a diagnosis of addiction in humans. Here, we studied transcriptional consequences of methamphetamine SA and repeated foot-shocks in rat brain.
Project description:Methamphetamine (METH) is a powerful stimulant that has caused addiction (compulsive drug seeking and taking behavior) in millions of people world-wide. METH abuse is also associated with negative impact on the brain. One feature of addiction is uncontrollable drug seeking despite adverse consequences and becomes habitual. To mimic this in a rat model, rats with a history of METH use are given the opportunity to earn METH accompanied by aversive shocks on their feet. Rats that continue to take METH are shock-resistant (SR) and rats that reduce their METH intake are shock-sensitive (SS ).Rats that self-administered saline are controls (CT). In addition, we used controls for shock paradigm. For this purpose, when METH SA rat received a shock, the saline SA rat was also shocked. The separate groups of rats that were yoked (Y) to the corresponding METH shock-resistant (SR) and shock-sensitive (SS) rats are termed YSR and YSS, respectively.
Project description:Methamphetamine is a widely abused, highly addictive drug. Regulation of synaptic proteins within the brain’s reward pathway modulates addiction behaviours, the progression of drug addiction and long-term changes in brain structure and function that result from drug use. Therefore, using large scale proteomics studies we aim to identify global protein expression changes within the dorsal striatum, a key brain region involved in the modulation of addiction. We performed LC-MS/MS analyses on rat striatal synaptosomes following 30 days of methamphetamine self-administration (2 hours/day) and 14 days abstinence. We identified a total of 84 differentially-expressed proteins with known roles in neuroprotection, neuroplasticity, cell cytoskeleton, energy regulation and synaptic vesicles. We identify significant expression changes in stress-induced phosphoprotein and protein Tppp, which have not previously been associated with addiction. In addition, we confirm the role of amphiphysin and phosphatidylethanolamine binding protein in addiction. This approach has provided new insight into the effects of methamphetamine self-administration on synaptic protein expression in a key brain region associated with addiction, showing a large set of differentially-expressed proteins that persist into abstinence.
Project description:Using ssRNA-seq, we examined the alteration of transcription profiles in the nucleus accumbens of methamphetamine-sensitized mice. Methamphetamine was a commonly abused psychostimulant. Repeated exposure to methamphetamine elicited long-lasting cellular and molecular changes, including the aberrant expression of coding and non-coding RNAs, which may involve in methamphetamine-induced locomotor sensitization and addiction.
Project description:Methamphetamine (METH) is a powerful stimulant that has caused addiction (compulsive drug seeking and taking behavior) in millions of people world-wide. METH abuse is also associated with negative impact on the brain. One feature of addiction is uncontrollable drug seeking despite adverse consequences and becomes habitual. To mimic this in a rat model, rats with a history of METH use are given the opportunity to earn METH accompanied by aversive shocks on their feet. Rats that continue to take METH are shock-resistant (SR) and rats that reduce their METH intake are shock-sensitive (SS ).Rats that self-administered saline are controls (CT). Thereafter, rats were injected intraperitoneally with the dopamine D1 receptor antagonist, SCH23390. SCH23390 caused substantial reduction of METH taking in a dose-dependent fashion. Stopping SCH23390 administration led to re-emergence of compulsive METH taking in the shock-resistant rats.
Project description:Addiction to psychostimulants is associated with neuroadaptive changes in various brain regions. In this experiment we use a model of methamphetamine self-administration during which we use footshocks as adverse consequences to divide rats into animals that continue to press an active lever to get the drug (shock-resistant) whereas other rats stop or significantly reduce pressing the lever (shock-sensitive) in the presence of these adverse consequences. To investigate potential molecular bases for the divergent phenotype, we performed a whole rat transcriptome study using Affymetrix rat arrays that cover more than 24,000 coding transcripts. The array experiments revealed that there were 24 differentially expressed genes between the resistant and sensitive rats, with 15 up- and 9 downregulated transcripts. Ingenuity pathway analysis revealed that these transcripts belong in a network of genes involved in nervous system development and function, cell signaling, behavior, and disorders of the basal ganglia. These genes included proenkephalin (PENK) and prodynorphin (PDYN), among others. Because PDYN and PENK are expressed in dopamine D1- and D2-containing NAc neurons, respectively, these findings suggest that mechanisms that impact both cell types may play a role in the regulation of compulsive methamphetamine taking by rats.
Project description:Neuroplastic changes in the dorsal striatum participate in the transition from casual drug use to habitual and compulsive drug taking. These alterations might also play a critical role in the development of methamphetamine (METH) addiction. Nevertheless, the molecular substrates that underlie habitual METH consumption have yet to be elucidated. Therefore, in the present study, we examined the influence of METH self-administration on the expression of genes and proteins of interest, as potential substrates of METH-induced neuronal plasticity in the dorsal striatum. Rats self-administered METH (0.1 mg/kg/injection, i.v.) during 15 h sessions for 8 d and were euthanized after 2 h, 24 h, or 1 month of abstinence. Compared to yoked saline control, METH self-administration induced increases in the mRNA expression of the transcription factors, c-fos and fosb, the neurotrophic factor, Bdnf, and of the synaptic protein, synaptophysin (Syp) at 2 h after cessation of drug exposure. METH self-administration also caused changes in FosB, BDNF and TrkB protein levels, with increases at 2 and 24 h but decreases observed after 1 month of drug abstinence. Importantly, METH exposure caused increases in the levels of H3K4me3 and pCREB after 2 and 24 h of abstinence. Chromatin immunoprecipitation followed by qPCR was used to clarify the role of these proteins in the regulation of gene expression. We found that METH self-administration caused enrichment of pCREB, but not of H3K4me3, on the promoters of c-fos, fosb, Bdnf and Syp at 2 h after drug cessation. These data indicate that METH-induced activation of their transcription is mediated, in part, by pCREB-dependent epigenetic phenomena. Thus, METH self-administration might trigger epigenetic changes that caused alterations in the expression of genes and proteins serving as substrates for addiction-related synaptic plasticity. Animals were trained to self-administer METH for 8 d as described in the paper, dorsal striata were isolated 2 h, 24 h and 1 month after the final self-administration session. RNA extraction, RNA labeling and microarray hybridization were performed. In brief, total RNA was isolated from the samples using RNeasy Mini Kit (QIAGEN, Valencia, CA). RNA concentration and integrity was determined using Agilent BioAnalyzer (Agilent, Santa Clara, CA). Samples were stored at -80ºC. Microarray hybridization was done using RatRef-12 Expression BeadChips arrays (22 523 probes) (Illumina Inc., San Diego, CA). A 600 ng of total RNA from each sample was amplified using Illumina RNA Amplification kit (Ambion, Austin, TX). Single-stranded RNA (cRNA) was generated and labeled by incorporating biotin-16-UTP (Roche Diagnostics, Indianapolis, IN). 750 ng of each cRNA sample were hybridized to Illumina arrays at 55°C overnight according to the Gene Expression Protocol for BeadStation (Illumina Inc.). Hybridized cRNA was detected with cyanine3-streptavidin (GE Healthcare, Piscataway, NJ) and quantified using Illumina's BeadStation 500GX scanner.
Project description:Despite addiction being one of the most prevalent and debilitating disorders worldwide, effective treatments are lacking. Repeated cocaine exposure induces maladaptive transcriptional regulation within the brainâ??s reward circuitry, such as the nucleus accumbens (NAc), and epigenetic mechanisms, such as histone acetylation or methylation on Lys (K) residues, have been linked to these lasting actions of cocaine. However, in contrast to K methylation, the functional role of histone Arg (R) methylation remains unexplored in addiction models and poorly understood in brain in general. Here we show that protein-R-methyltransferase-6 (PRMT6) and its associated histone mark, asymmetric dimethylation of R2 on histone H3 (H3R2me2a), are decreased in the NAc of mice and rats after repeated cocaine exposure, as well as in the NAc of cocaine-addicted humans. PRMT6 downregulation occurs selectively in NAc medium spiny neurons expressing dopamine D2 receptors (D2-MSNs) and serves to protect against cocaine-induced addictive-like behavioral abnormalities. Using ChIP-seq, we demonstrate that reduced H3R2me2a binding at gene targets in NAc after repeated cocaine is strongly correlated with increased binding of H3K4me3, and identify Src kinase signaling inhibitor 1 (Srcin1 or p140Cap) as a key gene for these chromatin modifications. Cocaine induction of Srcin1 in NAc, which is associated with reduced Src signaling, decreases cocaine reward, the motivation to self administer cocaine, and cocaine-induced changes in NAc MSN dendritic spines. These results suggest that this suppression of Src signaling in NAc D2-MSNs, via PRMT6 and H3R2me2a downregulation, functions as a homeostatic brake to restrain cocaine action, and provide novel candidates for the development of new treatments for cocaine addiction. H3R2me2A ChIP-seq of mouse. Cocaine vs Saline, 3 biological replicates.
Project description:Drug addiction is a major public health issue that is characterised by continued drug use despite negative consequences. However, the molecular and cellular mechanisms that underlie this behaviour are not well understood. In this study we investigated the role of miR-137, a microRNA that has been previously shown to control the expression of genes necessary for neuronal development and synapse maturation, with common variants in the MIR137 gene linked to a higher risk of schizophrenia. Previously, we revealed that miR-137 expression in cocaine-trained animals exhibited spatial and temporal variability in the dorsal striatum (DS). Building upon this observation, we hypothesised that augmenting miR-137 function in the DS would impact drug-seeking behavior under punishment conditions by modulating molecular targets involved in synaptic plasticity. Male Sprague-Dawley rats were trained to self-administer cocaine and then randomly assigned to receive either lentiviral-mediated overexpression of hsa-miR-137 (miR-137OE) or an empty pCDH-vector (pCDH-EV) control in the dorsomedial striatum (DMS). Once stable cocaine self-administration was achieved, drug-taking was assessed under conditions in which lever presses were associated with a 0.25 probability of foot shock (0.5 mA). During five days of testing, pCDH-EV control animals showed a significant reduction in responding for cocaine, whereas miR-137OE animals displayed greater resistance to the suppression of cocaine responding across foot shock sessions compared to controls. RNA-sequencing analysis of striatal tissue from miR-137OE animals revealed significant enrichment of genes involved in synaptic plasticity and astrocyte signalling compared to control animals. Taken together, these findings provide insight into the mechanisms underlying addiction risk and and contribute to a better understanding of the neural substrates involved in these disorders.