Contribution of Interoceptive Processing to Drug Reward and Withdrawal Aversion

University Of California, San Diego, La Jolla CA

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Abstract

Project 3: Substance abuse and dependence are enormous societal problems, with lifetime prevalence in adults greater than 15% in the United States. Despite significant recent advances in identifying critical neurobiological mechanisms underlying addiction, high rates of recidivism are seen with most biologically based treatments of substance dependence developed to date. Here we propose to examine the relatively unexplored role of interoception, the internal sense of the body, in regulation of drug-related urges, to provide a new conceptual framework from which novel treatment strategies may emerge. The overall goal of CIDIA is to elucidate the role of interoception in addiction, and Project 3 in particular examines the role of insular cortex for regulating drug-induced alterations in hedonic processing, potentially providing novel targets for addiction treatment. This animal project uses a direct insular cortex manipulation, silencing of rostral (agranular) or caudal (granular/dysgranular) insula through excessive inhibition with the GABAa agonist muscimol, to examine the causal role of interoceptive processing in: (1) the direct rewarding (euphorigenic) effects of d-amphetamine and morphine as measured by brain reward thresholds; (2) the dysphorigenic effects of withdrawal from acute or chronic dependence on these drugs as measured by brain reward thresholds; (3) the conditioned (learned) association between a novel environment paired with acute drug reward or withdrawal aversion as measured in a place conditioning paradigm. In this way, the animal study complements the human neuroimaging experiments of Projects 1 and 2 by ascertaining whether disruption of insula function alters hedonic processing along multiple dimensions: (1) positive (reward, euphoria) versus negative affect (aversion, dysphoria); (2) across time from initial drug exposure (acute reward and acute withdrawal) to chronic dependence; (3) direct versus conditioned hedonic processes; and (4) stimulant versus opioid effects. The results of these experiments will be used in the human projects to modify the neuroimaging paradigms to examine whether these differences can be observed in subjects in different stages of drug addiction. For example, the experimental paradigms used in Wave 2 of Projects 1 and 2 are contingent on Project 3 outcomes of insula silencing on positive versus negative direct / indirect reward-related effects. Importantly, the animal model will provide a causal test of the cross-sectional human imaging findings, which are correlational by nature. Finally, converging validity in both animal and human studies can lay the groundwork for a pre-clinical platform to examine treatments.