Methyl supplementation attenuates cocaine-seeking behaviors and cocaine-induced c-Fos activation in a DNA methylation-dependent manner.

Epigenetic mechanisms, such as histone modifications, regulate responsiveness to drugs of abuse, such as cocaine, but relatively little is known about the regulation of addictive-like behaviors by DNA methylation. To investigate the influence of DNA methylation on the locomotor-activating effects of cocaine and on drug-seeking behavior, rats receiving methyl supplementation via chronic l-methionine (MET) underwent either a sensitization regimen of intermittent cocaine injections or intravenous self-administration of cocaine, followed by cue-induced and drug-primed reinstatement. MET blocked sensitization to the locomotor-activating effects of cocaine and attenuated drug-primed reinstatement, with no effect on cue-induced reinstatement or sucrose self-administration and reinstatement. Furthermore, upregulation of DNA methyltransferase 3a and 3b and global DNA hypomethylation were observed in the nucleus accumbens core (NAc), but not in the medial prefrontal cortex (mPFC), of cocaine-pretreated rats. Glutamatergic projections from the mPFC to the NAc are critically involved in the regulation of cocaine-primed reinstatement, and activation of both brain regions is seen in human addicts when reexposed to the drug. When compared with vehicle-pretreated rats, the immediate early gene c-Fos (a marker of neuronal activation) was upregulated in the NAc and mPFC of cocaine-pretreated rats after cocaine-primed reinstatement, and chronic MET treatment blocked its induction in both regions. Cocaine-induced c-Fos expression in the NAc was associated with reduced methylation at CpG dinucleotides in the c-Fos gene promoter, effects reversed by MET treatment. Overall, these data suggest that drug-seeking behaviors are, in part, attributable to a DNA methylation-dependent process, likely occurring at specific gene loci (e.g., c-Fos) in the reward pathway.

Neuropeptide S facilitates cue-induced relapse to cocaine seeking through activation of the hypothalamic hypocretin system.

Drug addiction is a chronic relapsing disorder characterized by compulsive drug seeking and use. Environmental conditioning factors are among the major determinants of relapse in abstinent cocaine users. Here we describe a role of the neuropeptide S (NPS) system in regulating relapse. In rats with a history of cocaine self-administration, presentation of stimuli predictive of drug availability reinstates drug seeking, triggering relapse. Intracerebroventricular (ICV) injection of NPS increased conditioned reinstatement of cocaine seeking, whereas peripheral administration of the NPS receptor antagonist SHA 68 reduced it. Manipulation of the NPS receptor system did not modify cocaine self-administration. We also found that ICV NPS administration activates c-Fos expression in hypocretin-1/orexin-A (Hcrt-1/Ox-A) immunoreactive neurons in the lateral hypothalamus (LH) and in the perifornical area (PeF). Of note, intra-LH and intra-PeF administration of NPS increased conditioned reinstatement of cocaine responding, an effect that was selectively blocked with the Hcrt-1/Ox-A receptor selective antagonist SB334867. Finally, results showed that intra-LH injection of the NPS antagonist [D-Cys(tBu) (5)]NPS blocked cue-induced cocaine seeking, indicating a role for this system in the pathophysiology of drug relapse.

Mitochondrial impairment contributes to cocaine-induced cardiac dysfunction: Prevention by the targeted antioxidant MitoQ.

The goal of this study was to assess mitochondrial function and ROS production in an experimental model of cocaine-induced cardiac dysfunction. We hypothesized that cocaine abuse may lead to altered mitochondrial function that in turn may cause left ventricular dysfunction. Seven days of cocaine administration to rats led to an increased oxygen consumption detected in cardiac fibers, specifically through complex I and complex III. ROS levels were increased, specifically in interfibrillar mitochondria. In parallel there was a decrease in ATP synthesis, whereas no difference was observed in subsarcolemmal mitochondria. This uncoupling effect on oxidative phosphorylation was not detectable after short-term exposure to cocaine, suggesting that these mitochondrial abnormalities were a late rather than a primary event in the pathological response to cocaine. MitoQ, a mitochondrial-targeted antioxidant, was shown to completely prevent these mitochondrial abnormalities as well as cardiac dysfunction characterized here by a diastolic dysfunction studied with a conductance catheter to obtain pressure-volume data. Taken together, these results extend previous studies and demonstrate that cocaine-induced cardiac dysfunction may be due to a mitochondrial defect.

Sex steroid hormones, stress response, and drug craving in cocaine-dependent women: implications for relapse susceptibility.

Cocaine dependence is associated with an enhanced sensitivity to stress and drug craving. Increases in stress-induced craving and hypothalamic-pituitary-adrenal reactivity are also predictive of cocaine relapse outcomes. More important, sex differences in these responses have also been reported. To further understand the basis of the sex differences, the authors examined the influence of sex steroid hormones on subjective and physiological stress responses and drug craving in cocaine-dependent women. Women who had low progesterone levels (n=5) were compared with those with high progesterone levels (n=5) and with those with moderate levels of estradiol and progesterone (n=9) in their responses during exposure to stress, cocaine cues, and neutral imagery conditions. The high progesterone group showed significantly lower stress-induced and drug cue-induced cocaine craving ( p<.05) and reduced drug cue-induced anxiety levels ( p<.08) and lower drug cue-induced systolic and diastolic blood pressure levels compared with the low progesterone group. These data suggest that there are significant effects of sex steroid hormones on stress and drug cue-induced cocaine craving, anxiety, and cardiovascular responses. In particular, high progesterone during the midluteal phase of the cycle was associated with decreased stress-induced and drug cue-induced craving and decreased cue-induced anxiety and blood pressure responses. These findings are consistent with previous preclinical and clinical studies of progesterone's effects on the behavioral responses to cocaine and warrant further research to examine the effects of progesterone on stress-induced cocaine craving, stress arousal, and cocaine relapse susceptibility in women.

The neural correlates of cue-induced craving in cocaine-dependent women.

OBJECTIVE: Drug use reminders are associated with localized changes in brain activity related to intense drug wanting or craving in cocaine-dependent men. While cocaine dependence is prevalent and disabling in women, and certain clinically relevant sex differences exist, there is an absence of knowledge related to the neural correlates of cocaine craving in cocaine-dependent women. METHOD: The differential neural response to imagery depicting cocaine use and neutral imagery was defined by using [15O]H2O positron emission tomography (PET) imaging in eight cocaine-dependent women. Results were compared with a matched group of eight cocaine-dependent men. RESULTS: Cocaine-related imagery was associated with relative increases in cocaine craving and increases in regional cerebral blood flow in the superior temporal gyrus, dorsal anterior and posterior cingulate cortex, nucleus accumbens area, and the central sulcus. Compared with the results of an identical PET study in matched cocaine-dependent men, conditioned cocaine craving in women was associated with less activation of the amygdala, insula, orbitofrontal cortex, and ventral cingulate cortex and greater activation of the central sulcus and widely distributed frontal cortical areas. CONCLUSIONS: These findings suggest the presence of sex differences in the functional anatomy of cue-induced cocaine craving associated with drug dependence. Such differences may reflect sex differences in conditioned associations to cocaine use, in affective and other corollaries of cocaine craving, or in their volitional regulation and may underlie apparent sex differences in the effects of cocaine abstinence and the expectations of treatment outcome. Some support for the need for sex-specific strategies for treatment of cocaine dependence is also furnished by the findings of this study.

Hypothalamic-pituitary-adrenal axis and sympatho-adreno-medullary responses during stress-induced and drug cue-induced cocaine craving states.

RATIONALE: Environmental stimuli associated with cocaine are known to elicit drug craving and increase the likelihood of relapse. However, the psychobiological changes that occur with exposure to these stimuli and in episodes of drug craving are not well understood. This study examined the response of brain stress circuits to environmental stimuli that are known to increase cocaine craving in cocaine dependent individuals. METHODS: Fifty-four treatment seeking cocaine dependent individuals, who were admitted to an inpatient treatment research unit for 2-4 weeks, participated in three laboratory sessions. Subjects were exposed to a brief 5-min guided imagery procedure that involved imagining a recent personal stressful situation, a drug-related situation and a neutral-relaxing situation, one imagery per session presented in random order. Subjective ratings of craving and anxiety, cardiovascular measures, and plasma levels of adrenocorticotrophic hormone (ACTH), cortisol, prolactin, norepinephrine (NE) and epinephrine (EPI) were assessed. RESULTS: Exposure to stress and to drug cues each resulted in significant increases in cocaine craving and subjective anxiety, pulse rate, systolic blood pressure, ACTH, cortisol, prolactin and NE as compared to the response to neutral imagery. In addition, stress imagery also increased diastolic blood pressure and plasma EPI as compared to responses to the drug cue imagery and neutral-relaxing imagery. CONCLUSIONS: The findings indicate a significant activation of the CRF-HPA axis and noradrenergic/sympatho-adreno-medullary (SAM) system response during stress-induced and drug cue induced cocaine craving states in cocaine dependent individuals. The role of stress system activation in cocaine craving and in cocaine use is discussed.

Psychological stress, drug-related cues and cocaine craving.

RATIONALE: While several environmental situations may produce cocaine craving, there is little research on whether patterns of drug cue reactivity are similar across different environmental situations. OBJECTIVE: This study examined whether two different environmental situations, psychological stress and drug cues, produce similar or varying patterns of cue reactivity in 20 cocaine dependent individuals. METHODS: All subjects participated in a single laboratory session and were exposed to stress, drug cues and neutral-relaxing imagery conditions. Cocaine and alcohol craving, emotion state ratings, subjective anxiety, heart rate and salivary cortisol measures were assessed. RESULTS: Significant increases in cocaine and alcohol craving were observed with stress and drug cues imagery but not with neutral-relaxing imagery. In addition, stress and drug cues situations produced similar increases in subjective anxiety, heart rate and salivary cortisol levels. Significant increases in negative emotion ratings and decreases in positive emotion ratings were found for stress and drug cues conditions as compared to the neutral condition. CONCLUSIONS: The findings indicate that a similar and comparable pattern of cue reactivity is induced by stress and drug cue manipulations. Furthermore, the comparable increases in subjective anxiety and negative affect observed with stress-induced and drug cue-induced craving provides support for the negative reinforcement model of drug craving and relapse. The negative affectivity co-occurring with the craving state appears to be an important target in the development of new treatments for cocaine dependence.