Investigating the Central Amygdala Neuronal Proteome Mediating the Protective Effect of Social Reward on Incubation of Heroin Craving

Despite strides toward understanding circuit and molecular mechanisms of substance use disorders (SUDs), treatment options remain largely unchanged. This impasse is due, in part, to limitations in the construct and predictive validity of animal models of drug self-administration and relapse, which rarely incorporate social factors. In both humans and laboratory animals, adverse social interactions and social isolation promote drug self-administration and relapse, while positive social interaction tends to be protective. We recently developed an operant rat model of choice between drugs and social interaction and showed the profound protective effects of the latter on drug self-administration and relapse. Our research revealed two major findings. First, rats strongly prefer operant social interaction over heroin, methamphetamine (Meth), and cocaine. Additionally, social choice-induced abstinence (voluntary abstinence) decreases incubation (the progressive increase in drug seeking during abstinence) of heroin craving and prevents incubation of Meth craving. This protective effect was associated with activation of protein kinase-Cδ (PKCδ) in the central amygdala lateral part (CeL). In contrast, after forced abstinence, the reliable expression of incubation of Meth craving was associated with activation of CeL-somatostatin (SOM). The cellular and molecular mechanisms mediating the protective effect of social reward on heroin craving after voluntary abstinence remain unknown. Based on our preliminary data, we hypothesize that molecular changes within CeL PKCδ-expressing neurons in CeL are selective for the social-based buffering of incubation of heroin craving. In contrast, molecular changes within SOM-expressing neurons are selective for the forced abstinence-promoting expression of incubation of heroin craving. The overarching aim of this proposal is to elucidate changes in the neuronal proteome of CeL PKCδ/SOM- expressing neurons in heroin craving in order to understand the functional molecular pathways driving either the protective or promoting effects of voluntary versus forced abstinence procedures, respectively. By combining viral-mediated immunolabeling of CeL PKCδ-expressing neurons with laser capture microdissection (LCM) followed by isobaric tags for relative and absolute quantitation (iTRAQ), we predict differential protein expression as well as differential post translational modifications (PTMs) within the CeL PKCδ/SOM-expressing neurons during heroin craving after either voluntary or forced abstinence. Our proposal will provide new insights into the molecular mechanisms mediating the protective effect of social reward on addiction related measures merging cutting-edge tools for the investigation of neural circuits with an original behavioral model. This direction will provide collaborative potential and introduce new ideas and conceptual frameworks to the Yale/NIDA Neuroproteomics Center’s repertoire with potential direct translational applicability.