Neuroimaging and neuromodulation of preclinical models of substance use disorders

National Institute On Drug Abuse

Investigators

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Abstract

1. Frontostriatal regulation of brain circuits contributes to flexible decision making Deficits in behavioral or cognitive flexibility that are linked to altered activity in both cortical and subcortical brain regions, are often observed across multiple neuropsychiatric disorders. The medial prefrontal cortex (mPFC)-nucleus accumbens (NAc) pathway in rats plays a critical role in flexible control of behavior. However, the modulation of this pathway on activity and functional connectivity with the rest of the brain remains unclear. In this study, we first confirmed the role of the mPFC-NAc pathway in behavioral flexibility using a set-shifting task in rats and then evaluated the causal effects of mPFC-NAc activation induced by chemogenetic stimulation of the terminal axons of the NAc with DREADD expression on whole-brain activity and functional connectivity measured by functional MRI. mPFC-NAc activation improved performance on the set-shifting task by reducing perseverative errors. Additionally, stimulation of this pathway increased activity in a set of brain regions within the basal ganglia-thalamus-cortical loop network including NAc, thalamus, hypothalamus and various connected cortical regions, while also decreased functional connectivity strength of NAc-mPFC, NAc-secondary motor cortex (M2), and various cortical circuits. Moreover, performance on the set-shifting task was related to the functional connectivity strength of the above frontostriatal and cortical circuits. These findings provide insights into the link between specific frontostriatal circuits on decision making flexibility, which may inform potential future interventions for behavioral flexibility deficits. (Duan et al., Neuropsychopharmacology, 2025) 2. Cocaine self-administration increases impulsive decision-making in low-impulsive rats associated with impaired functional connectivity in the mesocorticolimbic system Impulsivity is often considered a risk factor for drug addiction; however, not all evidence supports this view. In the present study, we used a food reward delay-discounting task (DDT) to categorize rats as low-, middle-, and high-impulsive but failed to find any difference among these groups in the acquisition and maintenance of cocaine self-administration (SA), regardless of electrical footshock punishment. Additionally, there were no group differences in locomotor responses to acute cocaine in rats with or without a history of cocaine SA. Unexpectedly, chronic cocaine SA selectively increased impulsive choice in low-impulsive rats. Resting-state fMRI analysis revealed a positive correlation between impulsivity and cerebral blood volume in the midbrain, thalamus, and auditory cortex. Using these three regions as seeds, we observed a negative correlation between impulsivity and functional connectivity between the midbrain and frontal cortex, as well as between the thalamus and frontal cortex (including the orbitofrontal, primary, and parietal cortices) in low-impulsive rats. These correlations were attenuated following chronic cocaine SA. RNAscope in situ hybridization assays revealed a significant reduction in dopamine (DA) D1, D2, and D3 receptor mRNA expression in the corticostriatal regions of low-impulsive rats after cocaine SA. Our findings challenge the widely held view that impulsivity is a vulnerability factor for cocaine use disorder. Instead, chronic cocaine use appears to selectively increase impulsive choice decision-making in normally low-impulsive rats, associated with reduced functional connectivity and DA receptor expression in the mesocorticolimbic DA network. (Shen et al., eNeuro, 2025) 3. Functional MRI reveals regional changes of brain activity in rats following longitudinal focal high-density theta burst stimulation (hdTBS) Cocaine use disorder (CUD) has been linked to cortico-striatal dysfunctions, particularly within the prefrontal-striatal circuitry. However, previous studies have typically focused on discrete parcellations of the striatum, overlooking its continuous variations of neural organization. Moreover, while repetitive transcranial magnetic stimulation (rTMS) has shown benefits in CUD treatment, the neural effects of rTMS on striatal dysfunction in CUD remain poorly understood. Using connectome gradient-mapping techniques on three resting-state functional magnetic resonance imaging datasets, we derived the ventromedial-to-dorsolateral striatal functional topography. We identified specific alterations in this topography in the discovery cohort (41 CUD patients and 44 controls), validated findings in an independent cohort (53 CUD patients and 45 controls), and examined whether rTMS targeting the left dorsolateral prefrontal cortex (dlPFC) could normalize abnormalities in the rTMS-treatment cohort (44 patients). Across all datasets, we found a positive correlation between gradient variation and drug dependence severity in CUD. Compared to controls, CUD in both the discovery and replication cohorts exhibited elevated gradient values in the ventral striatum, while decreased values in the dorsal striatum were observed only in the discovery cohort. Furthermore, in the rTMS-treatment cohort, 5-Hz rTMS targeting the left dlPFC significantly normalized the aberrant gradient values in the ventral striatum, and these changes also related to cocaine craving changes. Overall, our study provides novel evidence of specific alterations in the ventromedial-to-dorsolateral functional topography of the striatum in CUD patients and highlights the impact of rTMS on striatal circuits through prefrontal modulation. (Li et al., Imaging Neuroscience, in press) 4. Role of claustrum in incubation of opioid seeking after electric barrier-induced voluntary abstinence in male and female rats We previously reported that ventral subiculum (vSub) activity is critical to incubation of oxycodone seeking after abstinence induced by adverse consequences of drug seeking. Here, we studied the role of claustrum, a key vSub input, in this incubation. We trained male and female rats to self-administer oxycodone for 2 weeks and then induced abstinence by exposing them to an electric barrier for 2 weeks. We used retrograde tracing (cholera toxin B subunit) plus the activity marker Fos to identify projections to vSub cactivated during “incubated” relapse (Abstinence Day 15). We then used pharmacological reversible inactivation to determine the causal role of claustrum in incubation and the behavioral and anatomical specificity of this role. We also used an anatomical disconnection procedure to determine the causal role of claustrum–vSub connections in incubation. Finally, we analyzed an existing functional MRI dataset to determine if functional connectivity changes in claustrum-related circuits predict incubation of oxycodone seeking. Claustrum neurons projecting to vSub were activated during relapse tests after electric barrier-induced abstinence. Inactivation of claustrum but not areas dorsolateral to claustrum decreased incubation of oxycodone seeking after electric barrier-induced abstinence; claustrum inactivation had no effect on incubation after food choice-induced abstinence. Both ipsilateral and contralateral inactivation of claustrum–vSub projections decreased incubation after electric barrier-induced abstinence. Functional connectivity changes in claustrum–cortical circuits during electric barrier-induced abstinence predicted incubated oxycodone relapse. Our study identified a novel role of claustrum in relapse to opioid drugs after abstinence induced by adverse consequences of drug seeking. (Negishi et al., J. Neuroscience, 2025)