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Title: Behavioural and cellular basis of the vulnerability to develop compulsive heroin seeking habits
Author: Fouyssac, Maxime
ISNI:       0000 0004 7231 851X
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2017
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Addiction is a chronic relapsing disorder for which there is no effective treatment. This may reflect our lack of understanding of the psychological and neural mechanisms that support the transition, in vulnerable individuals, from recreational drug use to compulsive drug seeking habits. Over the last decade clinical and preclinical studies have begun to shed light on the psychological and neural basis of the individual vulnerability to cocaine addiction, but despite the epidemic in opiates addiction in the USA and incremental opioid drug abuse and addiction in the UK, heroin addiction has hitherto been under-investigated. Using a novel preclinical model of compulsive heroin seeking behaviour in which some rats self-administering heroin persist in responding under a second-order schedule of reinforcement despite punishment (Chapter 3), the experiments in this thesis investigated the psychological, behavioural, neural and cellular mechanisms involved in the vulnerability to develop compulsive heroin seeking. Chapter 4 aimed to identify behavioural traits, such as anxiety, stress reactivity or decision making, that predict an increased vulnerability to develop compulsive heroin seeking. Chapter 5 aimed to characterise the neural and cellular correlates of heroin seeking habits, and compulsivity. Based on the combination of hotspot analysis, quantitative PCR, RNAscope and western-blot analyses, the data presented demonstrate that compulsive habits are associated with a differential pattern of cellular plasticity within corticostriatal networks, and are preceded by diverse cellular adaptations, especially in the striatum, in vulnerable individuals. Finally, chapter 6 further investigated the cellular specificity of the observed adaptations in experiments that revealed exposure to heroin and cocaine, triggers a downregulation of the dopamine transporter preferentially in astrocytes, and not in neurons as previously thought. The results presented in this thesis offer new insights into the neural and cellular basis of the vulnerability to develop compulsive heroin seeking, a key feature of opioid addiction.
Supervisor: Belin, David Sponsor: Cambridge Commonwealth ; European & International Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Addiction ; heroin ; preclinical model ; habits ; astrocytes