Role of Dorsomedial Striatum Neuronal Ensembles in Incubation of Methamphetamine Craving after Voluntary Abstinence

Abstract

We recently developed a rat model of incubation of methamphetamine craving after choice-based voluntary abstinence. Here, we studied the role of dorsolateral striatum (DLS) and dorsomedial striatum (DMS) in this incubation. We trained rats to self-administer palatable food pellets (6 d, 6 h/d) and methamphetamine (12 d, 6 h/d). We then assessed relapse to methamphetamine seeking under extinction conditions after 1 and 21 abstinence days. Between tests, the rats underwent voluntary abstinence (using a discrete choice procedure between methamphetamine and food; 20 trials/d) for 19 d. We used <i>in situ</i> hybridization to measure the colabeling of the activity marker <i>Fos</i> with <i>Drd1</i> and <i>Drd2</i> in DMS and DLS after the tests. Based on the <i>in situ</i> hybridization colabeling results, we tested the causal role of DMS D₁ and D₂ family receptors, and DMS neuronal ensembles in “incubated” methamphetamine seeking, using selective dopamine receptor antagonists (SCH39166 or raclopride) and the Daun02 chemogenetic inactivation procedure, respectively. Methamphetamine seeking was higher after 21 d of voluntary abstinence than after 1 d (incubation of methamphetamine craving). The incubated response was associated with increased <i>Fos</i> expression in DMS but not in DLS; <i>Fos</i> was colabeled with both <i>Drd1</i> and <i>Drd2</i>. DMS injections of SCH39166 or raclopride selectively decreased methamphetamine seeking after 21 abstinence days. In <i>Fos-lacZ</i> transgenic rats, selective inactivation of relapse test-activated <i>Fos</i> neurons in DMS on abstinence day 18 decreased incubated methamphetamine seeking on day 21. Results demonstrate a role of DMS dopamine D₁ and D₂ receptors in the incubation of methamphetamine craving after voluntary abstinence and that DMS neuronal ensembles mediate this incubation. <b>SIGNIFICANCE STATEMENT</b> In human addicts, abstinence is often self-imposed and relapse can be triggered by exposure to drug-associated cues that induce drug craving. We recently developed a rat model of incubation of methamphetamine craving after choice-based voluntary abstinence. Here, we used classical pharmacology, <i>in situ</i> hybridization, immunohistochemistry, and the Daun02 inactivation procedure to demonstrate a critical role of dorsomedial striatum neuronal ensembles in this new form of incubation of drug craving.