Sex differences in neural responses to stress and drug cues predicts future drug use in individuals with substance use disorder

BACKGROUND

Substance use disorders (SUDs) are chronically recurring illnesses, where stress and drug cues significantly increase drug craving and risk of drug use recurrence. This study examined sex differences in functional magnetic resonance imaging (fMRI) brain responses to stress and drug cue exposure and assessed their prospective association with future drug use post-treatment.

METHODS

Inpatient, treatment engaged men (N = 46) and women (N = 26) with SUDs, including alcohol, cocaine and/or cannabis use disorders, participated in an fMRI scan that assessed subjective (anxiety, drug craving), heart rate and neural responses to brief individualized script-driven imagery of stress, drug, and neutral-relaxing trials. Prospective follow-up interviews post-treatment assessed future drug use recurrence over 90 days.

RESULTS

During fMRI, stress and drug versus neutral cue exposure led to increased anxiety, heart rate and craving responses (p's < 0.004) in both men and women, but greater drug cue-induced anxiety (p < .017) and higher drug use days during follow-up (p < .006) in women relative to men. In whole brain analyses of stress and drug cues (p < .05 FWE corrected), and in whole brain correlation (p < .05, FWE corrected) with drug use days, significant sex differences revealed drug cue-related striatal hyperactivation (caudate, putamen) in men, but drug cue-related cortico-limbic (insula and dorsolateral prefrontal cortex) hypoactivation and stress-related hypoactivation in the ventromedial prefrontal cortex (VmPFC) in women; and these were significantly associated with higher future drug use days.

CONCLUSIONS

Findings indicate sex-specific pathophysiology of SUD recurrence and support the need for differential treatment development for men and women with SUD to improve drug use outcomes.

In a Rat Model of Opioid Maintenance, the G Protein-Biased Mu Opioid Receptor Agonist TRV130 Decreases Relapse to Oxycodone Seeking and Taking and Prevents Oxycodone-Induced Brain Hypoxia

BACKGROUND

Maintenance treatment with opioid agonists (buprenorphine, methadone) is effective for opioid addiction but does not eliminate opioid use in all patients. We modeled maintenance treatment in rats that self-administered the prescription opioid oxycodone. The maintenance medication was either buprenorphine or the G protein-biased mu opioid receptor agonist TRV130. We then tested prevention of oxycodone seeking and taking during abstinence using a modified context-induced reinstatement procedure, a rat relapse model.

METHODS

We trained rats to self-administer oxycodone (6 hours/day, 14 days) in context A; infusions were paired with discrete tone-light cues. We then implanted osmotic pumps containing buprenorphine or TRV130 (0, 3, 6, or 9 mg/kg/day) and performed 3 consecutive tests: lever pressing reinforced by oxycodone-associated discrete cues in nondrug context B (extinction responding), context-induced reinstatement of oxycodone seeking in context A, and reacquisition of oxycodone self-administration in context A. We also tested whether TRV130 maintenance would protect against acute oxycodone-induced decreases in nucleus accumbens oxygen levels.

RESULTS

In male rats, buprenorphine and TRV130 decreased extinction responding and reacquisition of oxycodone self-administration but had a weaker (nonsignificant) effect on context-induced reinstatement. In female rats, buprenorphine decreased responding in all 3 tests, while TRV130 decreased only extinction responding. In both sexes, TRV130 prevented acute brain hypoxia induced by moderate doses of oxycodone.

CONCLUSIONS

TRV130 decreased oxycodone seeking and taking during abstinence in a partly sex-specific manner and prevented acute oxycodone-induced brain hypoxia. We propose that G protein-biased mu opioid receptor agonists, currently in development as analgesics, should be considered as relapse prevention maintenance treatment for opioid addiction.

Eye tracking of smoking-related stimuli in tobacco use disorder: A proof-of-concept study combining attention bias modification with alpha-transcranial alternating current stimulation

BACKGROUND

Tobacco use disorder (TUD) is characterized by the presence of an attentional bias (AB) towards smoking-related stimuli. We investigated whether combining an AB modification paradigm (ABM) with transcranial alternating current stimulation (tACS) applied over the dorsolateral prefrontal cortex (DLPFC) reduces the AB towards smoking-related stimuli, as well as craving level and impulsive choices.

METHODS

In a sham-controlled, crossover preliminary study, 19 subjects with TUD received two stimulation arms: 1) active tACS (10 Hz, 2 mA, 30 min) combined with ABM and 2) sham tACS combined with ABM, in a randomized order, separated by one week. AB towards smoking cues during passive observation of smoking and neutral cues was assessed with an eye-tracking device and reactions times at a visual-probe task. Craving level was measured with the Questionnaire of Smoking Urges. Impulsive choices were assessed with the delay discounting task.

RESULTS

Active tACS combined with ABM reduced the amount of time spent looking at smoking-related pictures (p = 0.03), prevented the increase of self-reported desire to smoke (p = 0.026), and reduced the proportion of impulsive choices (p = 0.049), compared to sham tACS combined with ABM. No significant effects were reported on other craving dimensions and on AB based on reaction times.

CONCLUSIONS

These preliminary findings suggest that combining tACS with ABM may help smokers who wish to quit by reducing the desire to smoke, attention to smoking-cues, and impulsive decision-making.

What is abnormal about addiction-related attentional biases?

BACKGROUND

The phenotype of addiction includes prominent attentional biases for drug cues, which play a role in motivating drug-seeking behavior and contribute to relapse. In a separate line of research, arbitrary stimuli have been shown to automatically capture attention when previously associated with reward in non-clinical samples.

METHODS AND RESULTS

Here, I argue that these two attentional biases reflect the same cognitive process. I outline five characteristics that exemplify attentional biases for drug cues: resistant to conflicting goals, robust to extinction, linked to dorsal striatal dopamine and to biases in approach behavior, and can distinguish between individuals with and without a history of drug dependence. I then go on to describe how attentional biases for arbitrary reward-associated stimuli share all of these features, and conclude by arguing that the attentional components of addiction reflect a normal cognitive process that promotes reward-seeking behavior.

Outcome specificity in deepened extinction may limit treatment feasibility: co-presentation of a food cue interferes with extinction of cue-elicited cocaine seeking

BACKGROUND

We previously showed that presenting two cocaine cues simultaneously during extinction deepens the extinction of cue-elicited cocaine seeking (Kearns et al., 2012). The present study investigated whether compounding a non-drug appetitive cue with a cocaine cue would similarly deepen extinction.

METHODS

In Experiment 1, tone and click were each first established as discriminative stimuli for cocaine-reinforced responding and light was a cue for food-reinforced responding. In an initial extinction phase, all stimuli were presented individually. Then, during an additional compound extinction session, rats received 8 presentations of one of the cocaine cues (counterbalanced over subjects) simultaneously with light and 8 presentations of the other cue alone. A spontaneous recovery test was used to evaluate the effectiveness of the extinction treatments. Experiment 2 was performed under conditions designed to match those of Experiment 1, except food was the reinforcer in tone and click instead of cocaine.

RESULTS

In Experiment 1, the cocaine cue compounded with the food cue during extinction controlled greater spontaneous recovery of cocaine seeking than the cocaine cue always presented alone. In contrast, Experiment 2 demonstrated deepened extinction of responding to a food cue when both compounded cues were food cues.

CONCLUSIONS

Results suggest that deepened extinction depends on the compound presentation of cues associated with the same reinforcer. Compound presentation of cues associated with different reinforcers could lead to an enhancement of responding. Care is urged in attempts to deepen the extinction of cue-elicited drug seeking by compounding drug cues with non-drug cues.

Sex differences in cocaine/heroin users: drug-use triggers and craving in daily life

BACKGROUND

Studies of sex differences have shown that men and women with drug-use disorders differ in course and outcome and in cue-induced activation of putative brain "control network" areas. We evaluated sex differences in daily functioning and subjective events related to drug use with ecological momentary assessment (EMA).

METHODS

EMA data were collected from cocaine- and heroin-using outpatients (72 men; 42 women) in methadone maintenance in 2-5 randomly prompted (RP) entries per day and in participant-initiated entries for heroin or cocaine use or craving, for up to 25 weeks. Urine drug screens were conducted three times weekly. Data were analyzed via repeated-measures logistic regression, using sex as a predictor of responses.

RESULTS

In RP reports, women and men reported significantly different patterns of drug-cue exposure, with women significantly more likely to report having seen cocaine or been tempted to use in the past hour. Women also had higher craving after past-hour exposure to drug cues. In reports of drug use, women, compared to men, were more likely to report that they had used more cocaine than they had meant to, tended to feel guilty more often after drug use, and to have used despite trying not to use.

CONCLUSIONS

These findings provide real-time behavioral evidence that women respond differently than men to exposure to drug cues and to drug use, consistent with laboratory and brain-imaging findings. This information may be useful for development of sex-specific treatment strategies.