Restoration of a paraventricular thalamo-accumbal behavioral suppression circuit prevents reinstatement of heroin seeking.

Lack of behavioral suppression typifies substance use disorders, yet the neural circuit underpinnings of drug-induced behavioral disinhibition remain unclear. Here, we employ deep-brain two-photon calcium imaging in heroin self-administering mice, longitudinally tracking adaptations within a paraventricular thalamus to nucleus accumbens behavioral inhibition circuit from the onset of heroin use to reinstatement. We find that select thalamo-accumbal neuronal ensembles become profoundly hypoactive across the development of heroin seeking and use. Electrophysiological experiments further reveal persistent adaptations at thalamo-accumbal parvalbumin interneuronal synapses, whereas functional rescue of these synapses prevents multiple triggers from initiating reinstatement of heroin seeking. Finally, we find an enrichment of µ-opioid receptors in output- and cell-type-specific paraventricular thalamic neurons, which provide a mechanism for heroin-induced synaptic plasticity and behavioral disinhibition. These findings reveal key circuit adaptations that underlie behavioral disinhibition in opioid dependence and further suggest that recovery of this system would reduce relapse susceptibility.

Corticostriatal ensemble dynamics across heroin self-administration to reinstatement.

Corticostriatal projection neurons from prelimbic medial prefrontal cortex to the nucleus accumbens core critically regulate drug-seeking behaviors, yet the underlying encoding dynamics whereby these neurons contribute to drug seeking remain elusive. Here we use two-photon calcium imaging to visualize the activity of corticostriatal neurons in mice from the onset of heroin use to relapse. We find that the activity of these neurons is highly heterogeneous during heroin self-administration and seeking, with at least 8 distinct neuronal ensembles that display both excitatory and inhibitory encoding dynamics. These neuronal ensembles are particularly apparent during relapse, where excitatory responses are amplified compared to heroin self-administration. Moreover, we find that optogenetic inhibition of corticostriatal projection neurons attenuates heroin seeking regardless of the relapse trigger. Our results reveal the precise corticostriatal activity dynamics underlying drug-seeking behaviors and support a key role for this circuit in mediating relapse to drug seeking.