Astrocytes in the ventral pallidum extinguish heroin seeking through GAT-3 upregulation and morphological plasticity at D1-MSN terminals

Ariana Angelis,Danielle Dixon,Anna Kruyer,Peter W. Kalivas,Davide Amato

doi:10.1038/s41380-021-01333-5

Ariana Angelis, Danielle Dixon + Show 3 more

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https://doi.org/10.1038/s41380-021-01333-5

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Abstract

GABAergic projections from the nucleus accumbens core to the dorsolateral ventral pallidum are necessary for drug-conditioned cues to initiate relapse-like drug seeking. Astrocytes in the ventral pallidum are situated perisynaptically and regulate GABA transmission through expression of GABA uptake transporters, but whether they are involved in regulating drug seeking is unknown. To determine the contribution of ventral pallidal astrocytes to heroin seeking, we labeled astrocytes in male and female rats with a membrane-bound fluorescent tag and used confocal microscopy to quantify astroglial expression of the GABA transporter GAT-3 and astrocyte synaptic proximity after withdrawal from heroin self-administration and during 15 min of cued heroin seeking. We found that GAT-3 was upregulated in rats that had extinguished heroin seeking, but not in animals that were withdrawn from heroin without extinction training or in rats that extinguished sucrose seeking. When GAT-3 upregulation was reversed using a vivo-morpholino oligo, heroin seeking was restored in the extinguished context and extinction of cued heroin seeking was disrupted compared to control animals. Although astrocyte synaptic proximity was not altered overall after heroin withdrawal, examination of astrocyte proximity to accumbens D1- or D2-expressing afferents revealed a selective increase in astrocyte proximity with D1-expressing terminals during extinction of heroin self-administration. Experimentally-induced reduction of astrocyte synaptic proximity through knockdown of the astrocyte-selective actin-binding protein ezrin also markedly disrupted extinction of heroin seeking. Notably, GAT-3 or ezrin knockdown had no impact on context- or cue-induced seeking in sucrose-trained animals. These data show that astrocytes in the ventral pallidum undergo plasticity after extinction of heroin use that reduces seeking and highlight the importance of astrocyte-neuron interactions in shaping behaviors associated with opioid use disorder.

Highlights

Relapse vulnerability is a principal feature of opioid use disorder [1, 2] and activity in GABAergic projections from the nucleus accumbens core (NAcore) to the dorsolateral ventral pallidum is necessary for drug-associated cues to elicit drug seeking in rodent models of relapse [3, 4]
Our findings demonstrate that astrocytes in the dorsolateral ventral pallidum (dlVP) undergo subcircuit-selective morphological plasticity and changes in transporter expression that critically control the extinction of heroin seeking
Extinction of heroin self-administration upregulated GAT-3 expression in dlVP astrocytes Astroglia in the dlVP of male and female rats were transduced with AAV5.gfaABC1D.Lck.GFP (Fig. 1A, B) and trained to self-administer heroin for 10 × 3 h daily sessions

Summary

INTRODUCTION

Relapse vulnerability is a principal feature of opioid use disorder [1, 2] and activity in GABAergic projections from the nucleus accumbens core (NAcore) to the dorsolateral ventral pallidum (dlVP) is necessary for drug-associated cues to elicit drug seeking in rodent models of relapse [3, 4]. Astroglia markedly affect ongoing synaptic transmission in the adult rodent brain through changes in surface expression of transporters that remove synaptically released glutamate and GABA [20,21,22] and through their own structural plasticity, which impacts synaptic proximity of transporters expressed on astroglial peripheral processes [23,24,25]. 1234567890();,: terminate GABAergic synaptic transmission and regulate GABA microinjected (0.7 μL, 0.15 μL/min, 5 min diffusion) bilaterally in the dlVP spillover [29] Of these two, GAT-3 is expressed exclusively by astrocytes and is found largely on astroglial processes that serve to modulate tonic inhibitory currents in post-synaptic cells [22, 30, 31]. Cued heroin seeking was associated with a partial reversal of the extinction-induced increases in both GAT-3 and astrocyte proximity to D1-expressing synapses in the dlVP.

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