Opioid-induced cytokine release and glial activation has been proposed to directly contribute to the affective and physiological aspects of withdrawal. Furthermore, cytokine release following opioid administration has been hypothesized to be a limiting factor in both the duration and magnitude of opioid-induced analgesia. The two primary goals of our study are to assess AV411's ability to 1) reduce the opioid-withdrawal syndrome and 2) increase and prolong the analgesic effects of the mu-opioid agonist, oxycodone. To explore whether AV411 decreases opioid-induced glial cell activation, some participants assigned to the placebo and high dose AV411 groups (n = 6 for each dose condition) will be studied twice with [11C]PK11195, a positron emission tomography (PET) radiotracer used to measure the peripheral benzodiazepine receptor (PBR) in the human brain. The PBR is a receptor located on the mitochondria of the microglia and can be used to examine microglial activation in various brain regions.