Orbitofrontal cortex and dorsal striatum functional connectivity predicts incubation of opioid craving after voluntary abstinence

We recently introduced a rat model of incubation of opioid craving after voluntary abstinence induced by negative consequences of drug seeking. Here, we used resting-state functional MRI to determine whether longitudinal functional connectivity changes in orbitofrontal cortex (OFC) circuits predict incubation of opioid craving after voluntary abstinence. We trained rats to self-administer for 14 d either intravenous oxycodone or palatable food. After 3 d, we introduced an electric barrier for 12 d that caused cessation of reward self-administration. We tested the rats for oxycodone or food seeking under extinction conditions immediately after self-administration training (early abstinence) and after electric barrier exposure (late abstinence). We imaged their brains before self-administration and during early and late abstinence. We analyzed changes in OFC functional connectivity induced by reward self-administration and electric barrier–induced abstinence. Oxycodone seeking was greater during late than early abstinence (incubation of oxycodone craving). Oxycodone self-administration experience increased OFC functional connectivity with dorsal striatum and related circuits that was positively correlated with incubated oxycodone seeking. In contrast, electric barrier–induced abstinence decreased OFC functional connectivity with dorsal striatum and related circuits that was negatively correlated with incubated oxycodone seeking. Food seeking was greater during early than late abstinence (abatement of food craving). Food self-administration experience and electric barrier–induced abstinence decreased or maintained functional connectivity in these circuits that were not correlated with abated food seeking. Opposing functional connectivity changes in OFC with dorsal striatum and related circuits induced by opioid self-administration versus voluntary abstinence predicted individual differences in incubation of opioid craving.

Optimization of oscillated gas-liquid separator for simultaneous heavy metals determination in water sample

A technique has been developed to detect and determine multi heavy metals simultaneously in a water sample. Hydride generating technique was implemented to convert the analyte which present in the water sample (liquid phase) into another form with an improved separation coefficient, called “derivative”. This process occurred without changing the original chemical structure. Derivatives were separated from the liquid phase by applying custom made gas-liquid separator (GLS), operated with oscillation. Separated species then transferred into a die-electric barrier discharge (DBD) plasma atomizer where a fragmentation of the analyte into free atoms is occurred. The generated atoms were detected by emission spectroscopy. The presented technique was applied for detection of individual and multi heavy metals simultaneously in water sample and proved useful in terms of reducing the effect of the hydrogen generated, through the process, on suppressing the atoms signal in the DBD atomizer.

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

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.