Studies have shown that aberrant activity in some brain regions involved in the pathology of OCD overlaps similarly with individuals with addiction disorders. The reduced anxiety following a compulsion together with findings of diminished activation in the striatum during reward anticipation proposes a view of OCD being a behavior addiction. To investigate if there are consistent results across studies that support this view a systematic search of the literature was conducted. The keywords in the final search string used were: Obsessive-compulsive disorder, OCD, reward, risk, functional MRI, MRI, fMRI. Databases used for the search were Web of Science and PubMed. The inclusion criteria were studies that compared the neural activity during the anticipation phase of reward between OCD patients and healthy controls. The intervention and brain imaging used in the included studies were the monetary incentive delay task and fMRI. The main data extracted were the alterations in the striatum. Four studies were included in this review with inconsistent results. Three studies did not find any significant difference between OCD and healthy controls and therefore the findings in principle did not support the view of OCD being a behavior addiction. However, differences in study design between studies could be an explanation for the conflicting findings.

The rewarding properties of drugs in the mammalian system depend on their ability to activate appetitive motivational states. The associated underlying mechanism is strongly conserved in evolution and invertebrates have recently emerged as a powerful new model in addiction research. The natural reward system in crayfish has surprisingly proven sensitive to human drugs of abuse, providing a new model for research into the basic biological mechanisms of drug addiction. In this study, we examined the presence of natural reward systems in crayfish, and then characterized its sensitivity to 2.5 μg/g, 5.0 μg/g and 10.0 μg/g doses of methamphetamine (METH). Using the conditioned place preference (CPP) paradigm, we demonstrated that irrespective of the number of doses of METH injected into the pericardial system, crayfish seek out a particular tactile environment that had previously been paired with the METH. This study demonstrates that crayfish offer a comparative and complementary approach in addiction research. It contributes an evolutionary context to our understanding of a key component in learning and of natural reward as an important life-sustaining process.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第17988号 / 農博第2035号 / 新制||農||1019(附属図書館) / 学位論文||H26||N4813(農学部図書室) / 80832 / 京都大学大学院農学研究科食品生物科学専攻 / (主査)教授 伏木 亨, 教授 保川 清, 教授 安達 修二 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第18695号 / 農博第2092号 / 新制||農||1029(附属図書館) / 学位論文||H27||N4889(農学部図書室) / 31628 / 京都大学大学院農学研究科食品生物科学専攻 / (主査)教授 伏木 亨, 教授 河田 照雄, 教授 安達 修二 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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Alcohol-use disorders affect 15 million people nationwide, 4% of which are adolescents (12-17). Clinical data indicate that adolescents who binge drink greatly increase their likelihood of developing an alcohol-use disorder later in life. Moreover, research indicates that binge-drinking during adolescence produces long-lasting alterations in brain circuitry that underlie the processing of rewarding stimuli. The current study sought to determine the effect of adolescent exposure to chronic intermittent ethanol (AIE) on the consumption of, and motivation to obtain, sucrose solution in adulthood. Alcohol naïve, male Wistar rats arrived at the laboratory on post-natal day (PND) 25 and were randomly divided into two exposure groups (AIE and Air). Animals were provided 3 days to allow for acclimation to the animal colony, prior to the start or experimental procedure (PND 28). The AIE procedure involves inducing alcohol dependence by placing rats, in their home cage, into an alcohol vapor chamber for 14 consecutive days, with each exposure day consisting of 12 hrs of exposure in the chambers (8 am to 8 pm) and 12 hrs out of the chambers. The control rats (Air) are treated the same as AIE rats but without exposure to ethanol vapors. Following the AIE paradigm, all rats remained in their home-cage until adulthood (>PND 70) at which time they started operant training/testing in standard operant chambers equipped with two sipper tubes connected via tubing to liquid delivery solenoids. When the response requirement (# of licks) was met, animals received a delivery of 0.1 ml of 5% sucrose solution. All animals were instrumented to the operant procedure on a fixed-ratio (FR) 2 schedule which increased to an FR4 then FR8. Finally, all rats underwent a progressive ratio test in which response requirement increased exponentially for each liquid delivery. On lower schedules (FR2 and FR4) animals did not exhibit a significant difference in licks or reinforcers earned. However, for higher schedules (FR8 and PR) animals in the Air group exhibited a significantly higher level of behavior (licks) and received a significantly greater number of reinforcers than the AIE group. Overall, the data suggest that exposure to AIE, which approximates binge-like EtOH intake and dependence, differentially affects consumatory and appetitive behavior in response to a non-drug reward in adulthood.