Neuroscience: Behavioural effects of cocaine reversed

Gender-Specific Interactions in a Visual Object Recognition Task in Persons with Opioid Use Disorder

Opioid use disorder (OUD)-associated overdose deaths have reached epidemic proportions worldwide over the past two decades, with death rates for men reported at twice the rate for women. Using a controlled, cross-sectional, age-matched (18-56 y) design to better understand the cognitive neuroscience of OUD, we evaluated the electroencephalographic (EEG) responses of male and female participants with OUD vs. age- and gender-matched non-OUD controls during a simple visual object recognition Go/No-Go task. Overall, women had significantly slower reaction times (RTs) than men. In addition, EEG N200 and P300 event-related potential (ERP) amplitudes for non-OUD controls were significantly larger for men, while their latencies were significantly shorter than for women. However, while N200 and P300 amplitudes were not significantly affected by OUD for either men or women in this task, latencies were also affected differentially in men vs. women with OUD. Accordingly, for both N200 and P300, male OUD participants exhibited longer latencies while female OUD participants exhibited shorter ones than in non-OUD controls. Additionally, robust oscillations were found in all participants during a feedback message associated with performance in the task. Although alpha and beta power during the feedback message were significantly greater for men than women overall, both alpha and beta oscillations exhibited significantly lower power in all participants with OUD. Taken together, these findings suggest important gender by OUD differences in cognitive processing and reflection of performance in this simple visual task.

Natural and drug rewards act on common neural plasticity mechanisms with ΔFosB as a key mediator

Drugs of abuse induce neuroplasticity in the natural reward pathway, specifically the nucleus accumbens (NAc), thereby causing development and expression of addictive behavior. Recent evidence suggests that natural rewards may cause similar changes in the NAc, suggesting that drugs may activate mechanisms of plasticity shared with natural rewards, and allowing for unique interplay between natural and drug rewards. In this study, we demonstrate that sexual experience in male rats when followed by short or prolonged periods of loss of sex reward causes enhanced amphetamine reward, indicated by sensitized conditioned place preference for low-dose (0.5 mg/kg) amphetamine. Moreover, the onset, but not the longer-term expression, of enhanced amphetamine reward was correlated with a transient increase in dendritic spines in the NAc. Next, a critical role for the transcription factor ΔFosB in sex experience-induced enhanced amphetamine reward and associated increases in dendritic spines on NAc neurons was established using viral vector gene transfer of the dominant-negative binding partner ΔJunD. Moreover, it was demonstrated that sexual experience-induced enhanced drug reward, ΔFosB, and spinogenesis are dependent on mating-induced dopamine D1 receptor activation in the NAc. Pharmacological blockade of D1 receptor, but not D2 receptor, in the NAc during sexual behavior attenuated ΔFosB induction and prevented increased spinogenesis and sensitized amphetamine reward. Together, these findings demonstrate that drugs of abuse and natural reward behaviors act on common molecular and cellular mechanisms of plasticity that control vulnerability to drug addiction, and that this increased vulnerability is mediated by ΔFosB and its downstream transcriptional targets.