Role of ventral subiculum neuronal ensembles in incubation of oxycodone craving after electric barrier-induced voluntary abstinence

Abstract

We recently developed a rat model of incubation of oxycodone craving where opioid seeking progressively increases after voluntary suppression of drug self-administration by adverse consequences of drug seeking. Here, we studied the role of ventral subiculum (vSub) neuronal ensembles in this incubation, using the activity marker Fos, muscimol-baclofen (GABAergic agonists) inactivation, and Daun02 chemogenetic inactivation.We trained Sprague-Dawley or Fos-lacZ transgenic male and female rats to self-administer oxycodone (0.1 mg/kg/infusion, 6-h/d) for 14 days. The rats were then exposed for 14 days to an electric barrier of increasing intensity (0.1 to 0.4 mA) near the drug-paired lever that caused voluntary abstinence or were exposed to 14 days of forced abstinence. We tested Sprague-Dawley rats for relapse to oxycodone seeking without shock and drug on abstinence day 15 and extracted their brains for Fos-immunohistochemistry, or tested them after vSub vehicle or muscimol-baclofen injections on abstinence days 1 and 15. We performed Daun02 inactivation of relapse-activated vSub Fos neurons in Fos-lacZ transgenic rats on abstinence day 15 and then tested them for relapse on abstinence day 18.Relapse after electric barrier-induced abstinence increased Fos expression in vSub. Muscimol-baclofen inactivation or Daun02 selective inactivation of vSub Fos-expressing neuronal ensembles decreased “incubated” oxycodone seeking after voluntary abstinence. Muscimol-baclofen vSub inactivation had no effect on non-incubated opioid seeking on abstinence day 1 or incubation after forced abstinence.Our results demonstrate a selective role of vSub neuronal ensembles in incubation of opioid craving after cessation of drug self-administration by adverse consequences of drug seeking.Significance statementHigh relapse rate is a cardinal feature of opioid addiction and a major impediment for successful treatment. In humans, abstinence is often self-imposed, and relapse typically involves a conflict situation between the desire to experience the drug’s rewarding effects and negative consequences of drug seeking. To mimic this human condition, we recently introduced a rat model of incubation of oxycodone craving after electric barrier-induced voluntary abstinence. Here, we used the activity marker Fos, muscimol-baclofen (GABAergic agonists) inactivation, and Daun02 chemogenetic inactivation to demonstrate a selective role of vSub neuronal ensembles in incubation of oxycodone craving after electric barrier-induced voluntary abstinence, but not in incubation of opioid craving after forced abstinence or non-incubated opioid seeking during early abstinence.

Animal Models of Drug Relapse and Craving after Voluntary Abstinence: A Review

“…Evidence from recent studies suggests that this is also the case for voluntary abstinence relapse models. Thus, inhibition of vSub decreases both context-induced relapse to alcohol seeking after punishment and incubation of opioid seeking after electric barrier-induced abstinence Fredriksson et al, 2021). Additionally, inhibition of AI decreases relapse to both fentanyl and methamphetamine seeking after food choice-induced abstinence (Venniro et al, 2017a;Reiner et al, 2020).…”

“…In another study, Fredriksson et al (2021) determined the role of vSub in incubation of oxycodone seeking after electric barrier-induced abstinence in male and female rats. They tested the rats for relapse to oxycodone seeking on abstinence day 15 and extracted their brains for Fos immunohistochemistry or tested the rats after vSub injections of vehicle or muscimol 1 baclofen on abstinence day 1 or day 15 after forced or electric barrier-induced abstinence.…”

“…In the case of the electric barrier-induced abstinence model, much less is known about the brain areas controlling relapse in this model. Fredriksson et al (2021) showed that inhibition of vSub decreases incubated oxycodone seeking after electric barrier-induced abstinence. This finding agrees with previous studies showing that inhibition of vSub decreases context-induced reinstatement of heroin seeking (Bossert and Stern, 2014) after extinction and context-induced relapse of alcohol seeking after punishment (Marchant et al, 2016).…”

Incubation of Oxycodone Craving Following Adult-Onset and Adolescent-Onset Oxycodone Self-Administration in Male Rats

“…In both studies, we found no age differences in oxycodone selfadministration in rats at a dose of 0.1 mg/kg under extended access condition (6 h/day). We chose this experimental condition based on previous studies from us and others detecting reliable oxycodone self-administration and incubation of oxycodone craving in adult rats (Fredriksson et al, 2020(Fredriksson et al, , 2021Altshuler et al, 2021). In contrast, an early dose-response study showed that adolescent mice self-administered less oxycodone than adult mice across various doses (Zhang et al, 2009).…”

“…One of the main barriers to addressing this opioid epidemic is the prevalence of relapse to drug use ( Gostin et al, 2017 ; Kariisa et al, 2019 ), often triggered by re-exposure to drug-associated cues ( O’Brien et al, 1986 ). Recently, we and others demonstrated that oxycodone seeking in adult rats progressively increases after abstinence from oxycodone self-administration ( Fredriksson et al, 2020 , 2021 ; Altshuler et al, 2021 ). This incubation of craving phenomenon has also been previously observed in rats with a history of cocaine ( Grimm et al, 2001 ), heroin ( Shalev et al, 2001 ), nicotine ( Abdolahi et al, 2010 ), alcohol ( Bienkowski et al, 2004 ), methamphetamine ( Shepard et al, 2004 ), and sucrose ( Grimm et al, 2005 ) self-administration.…”