Project description:One of the major challenges of cocaine addiction is the high rate of relapse to drug use after periods of withdrawal. During the first few weeks of withdrawal, cue-induced cocaine craving intensifies, or "incubates," and persists over extended periods of time. Although several brain regions and molecular mechanisms were found to be involved in this process, the underlying epigenetic mechanisms are still unknown. Herein, we used a rat model of incubation of cocaine craving, in which rats were trained to self-administer cocaine (0.75 mg/kg, 6 h/d, 10 d), and cue-induced cocaine-seeking was examined in an extinction test after 1 or 30 d of withdrawal. We show that the withdrawal periods, as well as cue-induced cocaine seeking, are associated with broad, time-dependent enhancement of DNA methylation alterations in the nucleus accumbens (NAc). These gene methylation alterations were partly negatively correlated with gene expression changes. Furthermore, intra-NAc injections of a DNA methyltransferase inhibitor (RG108, 100 μm) abolished cue-induced cocaine seeking on day 30, an effect that persisted 1 month, whereas the methyl donor S-adenosylmethionine (500 μm) had an opposite effect on cocaine seeking. We then targeted two proteins whose genes were demethylated by RG108-estrogen receptor 1 (ESR1) and cyclin-dependent kinase 5 (CDK5). Treatment with an intra-NAc injection of the ESR1 agonist propyl pyrazole triol (10 nm) or the CDK5 inhibitor roscovitine (28 μm) on day 30 of withdrawal significantly decreased cue-induced cocaine seeking. These results demonstrate a role for NAc DNA methylation, and downstream targets of DNA demethylation, in incubation of cocaine craving.
Project description:DNA methylation profiling of nucleus Accumbens of rats that self administered cocaine and were subjected to 1 or 30 withdrawal days with or without extinction tests. The groups consist of 1. Saline rats (Sal.) 2. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 1 day (1W) 3. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 1 day and to an extinction test for assessment of cue-induced cocaine-seeking behavior (1C) 4. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 30 days (30W) 5. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 30 days and to an extinction test for assessment of cue-induced cocaine-seeking behavior (30C)
Project description:DNA methylation profiling of nucleus Accumbens of rats that self administered cocaine and were subjected to 1 or 30 withdrawal days with or without extinction tests.
Project description:In the 'incubation of cocaine craving' model of relapse, rats exhibit progressive intensification (incubation) of cue-induced craving over several weeks of forced abstinence from cocaine self-administration. The expression of incubated craving depends on plasticity of excitatory synaptic transmission in nucleus accumbens core (NAcC) medium spiny neurons (MSN). Previously, we found that the maintenance of this plasticity and the expression of incubation depends on ongoing protein translation, and the regulation of translation is altered after incubation of cocaine craving. Here we used male and female rats that express Cre recombinase in either dopamine D1 receptor- or adenosine 2a (A2a) receptor-expressing MSN to express a GFP-tagged ribosomal protein in a cell-type specific manner, enabling us to use Translating Ribosome Affinity Purification (TRAP) to isolate actively translating mRNAs from both MSN subtypes for analysis by RNA-seq. We compared rats that self-administered saline or cocaine. Saline rats were assessed on abstinence day (AD) 1, while cocaine rats were assessed on AD1 or AD40-50. For both D1-MSN and A2a-MSN, there were few differentially translated genes between saline and cocaine AD1 groups. In contrast, pronounced differences in the translatome were observed between cocaine rats on AD1 and AD40-50, and this was far more robust in D1-MSN. Notably, all comparisons revealed sex differences in translating mRNAs. Sequencing results were validated by qRT-PCR for several genes of interest. This study, the first to combine TRAP-seq, transgenic rats, and a cocaine self-administration paradigm, identifies translating mRNAs linked to incubation of cocaine craving in D1-MSN and A2a-MSN of the NAcC.
Project description:DNA methylation profiling of nucleus Accumbens of rats that self administered cocaine, were subjected to 30 withdrawal days, were treated with aCSF, RG108 or SAM and were subjected to extinction tests. The groups consist of: 1. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 30 days, were injected in the nucleus accumbens with aCSF and were subjected to an extinction test for assessment of cue-induced cocaine-seeking behavior (aCSF) 2. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 30 days, were injected in the nucleus accumbens with RG108 and were subjected to an extinction test for assessment of cue-induced cocaine-seeking behavior (RG108) 3. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 30 days, were injected in the nucleus accumbens with SAM and were subjected to an extinction test for assessment of cue-induced cocaine-seeking behavior (SAM)
Project description:DNA methylation profiling of nucleus Accumbens of rats that self administered cocaine, were subjected to 30 withdrawal days, were treated with aCSF, RG108 or SAM and were subjected to extinction tests.
Project description:Gene expression profiling of nucleus Accumbens of rats that self administered cocaine and were subjected to 1 or 30 withdrawal days with or without extinction tests. The groups consist of 1. Saline rats (Sal.) 2. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 1 day (1W) 3. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 1 day and to an extinction test for assessment of cue-induced cocaine-seeking behavior (1C) 4. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 30 days (30W) 5. Rats that self-administered cocaine for 10 days and that were subjected to a withdrawal period of 30 days and to an extinction test for assessment of cue-induced cocaine-seeking behavior (30C)
Project description:Gene expression profiling of nucleus Accumbens of rats that self administered cocaine and were subjected to 1 or 30 withdrawal days with or without extinction tests.
Project description:Relapse to cocaine use after prolonged abstinence is an important clinical problem. This relapse is often induced by exposure to cues associated with cocaine use. To account for the persistent propensity for relapse, it has been suggested that cue-induced cocaine craving increases over the first several weeks of abstinence and remains high for extended periods. We and others identified an analogous phenomenon in rats that was termed 'incubation of cocaine craving': time-dependent increases in cue-induced cocaine-seeking over the first months after withdrawal from self-administered cocaine. Cocaine-seeking requires the activation of glutamate projections that excite receptors for alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) in the nucleus accumbens. Here we show that the number of synaptic AMPA receptors in the accumbens is increased after prolonged withdrawal from cocaine self-administration by the addition of new AMPA receptors lacking glutamate receptor 2 (GluR2). Furthermore, we show that these new receptors mediate the incubation of cocaine craving. Our results indicate that GluR2-lacking AMPA receptors could be a new target for drug development for the treatment of cocaine addiction. We propose that after prolonged withdrawal from cocaine, increased numbers of synaptic AMPA receptors combined with the higher conductance of GluR2-lacking AMPA receptors causes increased reactivity of accumbens neurons to cocaine-related cues, leading to an intensification of drug craving and relapse.