La contribution de la neurotransmission dopaminergique dans le noyau accumbens à l’effet de récompense induit par la stimulation électrique du cerveau a été l’objet de plusieurs années de recherche. Cependant, d’autres sites recevant des terminaisons dopaminergiques pourraient contribuer à moduler la récompense dans d’autres régions cérébrales. Parmi elles, on retrouve l’habenula qui reçoit des projections dopaminergiques de l’aire tegmentale ventrale. La contribution de cette voie au phénomène de récompense en général et à l’effet de recompense induit par l’autostimulation intracrânienne est peu connue. Le but de cette recherche était d’étudier la contribution de la dopamine mésohabenulaire à l’effet de recompense induit par la stimulation électrique du raphé dorsal. Des rats ont été implantés d’une bicanule dans l’Hb et d’une électrode dans le raphé dorsal. Le paradigme du déplacement de la courbe a été utilisé pour évaluer les changements dans l’effet de récompense à la suite de l’injection intra-habenulaire d’amphétamine (10-40 μg). À titre de contrôles positifs, des rats ont reçu l’amphétamine dans le core et dans le shell (1-20 μg) du noyau accumbens. Les injections d’amphétamine dans l’habenula n’ont pas changé l’effet de récompense induit par la stimulation électrique. Dans le noyau accumbens, les injections dans le shell et le core provoquent des augmentations dans l’effet de récompense comme il a déjà été démontré. Nos résultats suggèrent que la neurotransmission dopaminergique dans l’habenula latérale ne contribue pas significativement au circuit soutenant l’effet renforçant de la stimulation électrique du cerveau. / The contribution of nucleus accumbens dopamine neurotransmission to reward and reinforcement has been the focus of many years of study. Other terminal sites have received comparatively less research attention, but may be potentially important. One of these sites is the lateral habenula, which receives dopaminergic innervation from cells arising from the ventral tegmental area. Very little is known about the contribution of this pathway to reward in general and to the rewarding effect of electrical brain stimulation in particular. The goal of this study was to study the contribution of mesohabenular dopamine to reward induced by electrical stimulation of the dorsal raphe. Male Sprague-Dawley rats were implanted with bilateral cannulae in the lateral habenula and a stimulation electrode aimed at the dorsal raphe nucleus. Using the curveshift paradigm, we measured the rewarding effect of intra-habenular infusions of amphetamine (10-40 μg). Control rats received amphetamine infusions into nucleus accumbens core or shell subregions (1-20 μg). Our findings show that regardless of concentration, intra-habenular amphetamine did not alter brain stimulation reward. Infusions into the nucleus accumbens enhanced the rewarding effectiveness of the stimulation, as previously shown. Our findings suggest that dopaminergic neurotransmission within the lateral habenula does not contribute significantly to the circuitry that mediates the rewarding effect of electrical brain stimulation.

Alcoholism is a persistent substance abuse disorder that is associated with negative health, social, and economic outcomes. Treatment strategies for alcohol use disorders are limited, and only three drugs have been approved by the FDA for treatment. Although behavioral therapy and drug combination strategies improve abstinence outcomes, the majority of those in treatment will not achieve long-term abstinence. Therefore, better treatment strategies are needed. While much progress has been made toward understanding the neurobiology of alcoholism, this knowledge has not been effectively translated into treatment strategies. Animal models of alcohol drinking have been crucial to this research effort, but until recently there have been few procedures that effectively model alcoholism by producing binge-like drinking, withdrawal, and relapse behavior. In the last five years the intermittent alcohol access (IAA) model, which uses repeated cycles of scheduled alcohol deprivation and reinstatement to elevate drinking, has been established as such a procedure, with substantial evidence that escalation of drinking produced by IAA is mediated by similar mechanisms as in human alcoholics, which include transcriptional regulation that alters functioning of mesolimbocortical reward pathways. The IAA model. The studies reported herein characterize changes in gene expression in mesolimbocortical brain regions associated with development of maladaptive binge-like alcohol drinking due to scheduled abstinence, particularly in the nucleus accumbens, which regulates motivated behavior. Furthermore the IAA model is characterized with regard to effectiveness in 2 ethanol-preferring C57BL/6 inbred mouse strains, and the influence of concurrent access to multiple alcohol concentrations is examined. Finally, the potential of naltrexone and novel mu-opioid receptor-selective antagonist NAQ to modulate alcohol drinking under continuous access and intermittent access procedures is reported. Microarray analysis is used to analyze the transcriptome in prefrontal cortex, nucleus accumbens, and ventral midbrain of C57BL/6NCrl mice after alcohol deprivation, and to identify differentially expressed genes and gene co-expression networks in C57BL/6J mice during continuous access, as well as after six cycles of IAA. Differentially expressed genes, network hub genes, and regulation mechanisms represent high priority targets for further study in binge-like drinking behavior, with the goal of translating this knowledge to treatment strategies for alcoholism.

No description available.

O núcleo acumbens (Acb) é subdividido em core e shell (AcbSh). Há evidências que as divisões do Acb vão além da dicotomia core-shell e que regiões pobres em tirosina hidroxilase (TH) e calretinina (Calr) formam um sistema de corredores no AcbSh. Para detalhar melhor a organização do Acb investigamos a distribuição de TH, Calr, DARPP-32 e do transportador de dopamina (DAT). Em seguida, foi comparada a distribuição destes marcadores com a das subunidades GluA2/3 dos receptores de glutamato do tipo AMPA. Finalmente, exploramos se as aferências pré-frontais são direcionadas à distintos compartimentos do AcbSh. Nossos resultados revelaram que regiões que contém neurônios GluA2/3+ intensamente marcados formam um sistema de corredores no AbSh que coincide com áreas pobres em TH, Calr e DAT. Os experimentos de rastreamento anterógrado indicaram que somente uma pequena parte das aferências pré-frontais é direcionada aos corredores. Nossos resultados delinearam um sistema de corredores no AcbSh que provavelmente constitui um compartimento neuroquímico altamente especializado. / The nucleus accumbens (Acb) is subdivided in core and shell (AcbSh). There is evidence that accumbal subdivisions go beyond this core-shell dichotomy and that regions poor in tyrosine hydroxylase (TH) and calretinin (Calr) form a corridor system in the Acbsh. To better detail accumbal organization, we investigated the distribution of TH, Calr, DARPP-32 and of the dopamine transporter (DAT). Then we compared the distribution of these markers with that of the AMPA-type glutamate receptor subunits GluA2/3. Finally, we explored whether prefrontal afferents are directed to distinct AcbSh compartments. Our findings revealed that regions containing intensely labeled GluA2/3+ neurons form a corridor system in the AcbSh that coincides with regions poor in TH, Calr, and DAT. Anterograde tracing experiments indicated that only a small portion of the prefrontal afferents is specifically related to the corridors. Our findings delineated a complex corridor system in the AcbSh which might constitute a highly specialized neurochemical compartment.

A dependência de drogas é um transtorno multifatorial complexo que se desenvolve em uma minoria de indivíduos que fazem uso dessas substâncias. Memórias associativas entre a droga e o contexto funcionam como gatilho para disparar comportamentos não adaptativos de busca e consumo, além de recaídas após períodos de abstinência. Subjacentes a essas mudanças comportamentais, existem modificações nas subunidades de receptores glutamatérgicos do tipo AMPA em estruturas envolvidas com memória (Hipocampo) e recompensa (Núcleo Accumbens). Por isso, estratégias que enfraqueçam a associação do contexto com a droga e que aprofundem o conhecimento dos circuitos envolvidos nesses comportamentos são de extrema relevância terapêutica. A memória quando evocada pode passar por dois processos pós-evocação: a extinção, em que uma nova memória é formada inibindo uma prévia associação, e a reconsolidação, em que a memória original entra em um estado lábil e suscetível a modificações, em que é possível enfraquecê-la através da inibição de sua reconsolidação. A reconsolidação da memória mostra-se uma estratégica mais eficaz e duradoura em relação à extinção, já que a memória original é modificada. Como modelo animal para o estudo da memória na dependência de drogas, o condicionamento de preferência por local (CPL) é bastante utilizado e sabe-se que é possível enfraquecer a preferência através do bloqueio da reconsolidação. Porém, são escassos os estudos que investigaram a existência da reconsolidação no modelo de sensibilização locomotora, que parece ocorrer, na maioria dos casos, em condição dependente do contexto de aquisição do comportamento, embora existam exemplos que demonstrem sua independência. As questões a serem respondidas neste trabalho são (a) se é possível reverter conjuntamente a preferência por local e a sensibilização locomotora à morfina (5 mg/kg) em ratos Wistar adultos machos, inibindo-se a síntese proteica com cicloheximida (CHX) i.p. logo após uma sessão de reativação contextual da memória no CPL, (b) se a reversão dos comportamentos reflete alterações (já descritas por outros autores) em GluA1, GluA1p (Ser845) e GluA2, no Hipocampo dorsal (HPCd) e no Núcleo Accumbens (NAc), e (c) se o mesmo tratamento em ambas estruturas reverte os dois parâmetros avaliados – comportamental e neuroquímico – de forma diferente ou igual. Nossos resultados mostraram ser possível reverter a preferência por local e a sensibilização locomotora por inibição sistêmica de síntese proteica, e que o condicionamento com exposição à morfina induz alterações nas subunidades analisadas de AMPA, conforme verificado no HPCd e NAc, embora a CHX não tenha produzido um efeito tão bem definido. Os animais que receberam infusões centrais no HPCd e NAc (central) não exibiram preferência por local, nem sensibilização. Em conjunto, nossos resultados mostraram, pela primeira vez em um mesmo desenho experimental, que é possível reverter diferentes aspectos da memória de recompensa (preferência e sensibilização) por meio do bloqueio da reconsolidação. / Drug addiction is a complex and multifactorial disorder that develops in a few people who use these substances. Associative memories between the drug and context of use act as a trigger for maladaptive behavior such as drug seeking and drug use, in addition to relapse after an extended period of withdrawal. Underlying these behavioral changes are modifications in glutamatergic reception (AMPA) in structures involved with memory (Hippocampus) and reward (Nucleus Accumbens). Therefore, strategies that weaken the drug and context association and deepen knowledge of circuits involved in these behaviors are extremely relevant therapeutically. When retrieved, a memory can undergo two distinct processes post-retrieval: extinction, in which a new memory inhibiting a previous association is generated, and reconsolidation, in which the original memory can enter a labile state and is susceptible to modifications, when it can be weakened by inhibition of its reconsolidation. Reconsolidation of memory has been shown to be a more effective and long lasting strategy in relation to extinction, since the original memory is modified. An animal model for studying drug addiction, conditioned place preference (CPP) is largely used and it is well known that it is possible to weaken preference by disrupting reconsolidation. However, there are few studies that investigate the existence of reconsolidation in a locomotor sensitization paradigm, which seems to occur in a condition dependent on context of acquisition, although some works report its independence. The questions answered in this work were (a) if it is possible to reverse both, context preference and locomotor sensitization to morphine (5mg/kg) by protein synthesis inhibition (CHX) after a contextual memory reactivation session in CPP, (b) if the disruption of behaviors reflects a reversal of changes of GluA1, GluA1p (Ser845) e GluA2 in dorsal Hippocampus (dHPC) and Nucleus Accumbens (NAc) and (c) if the same treatment in these structures differentially reverts the two parameters assessed. Our results indicate that it is possible to revert context preference and locomotor sensitization via systemic disruption of protein synthesis and that morphine conditioning induces changes in AMPA subunits in dHPC and NAc, although CHX did not have an evident effect on molecular reversal. Animals cannulated in dHPC and NAc core did not induce preference or sensitization. Taken together, our results demonstrated, for the first time, using the same experimental design that is possible to revert different aspects of reward memory (preference and sensitization) by disrupting the reconsolidation process.

L'impulsivité, un trait multidimensionnel, détermine la sévérité d'affections comportant des désordres compulsifs (syndrome de Gilles de la Tourette, maladie de Parkinson, troubles obsessionnels compulsifs), mais la nature de la relation impulsivité / compulsivité reste méconnue. L'intérêt du présent travail est d'identifier les substrats neurobiologiques de la balance impulsivité / compulsivité, dans une approche transnosographique, en s'aidant au plan préclinique, de manipulations causales et au plan clinique, d'une approche corrélationnelle. Ainsi, nous démontrons pour la première fois en dehors du champ de l'addiction, non seulement que l'impulsivité motrice, endophénotype de vulnérabilité à la compulsivité, prédit, sous l'influence de la transmission noradrénergique, la transition vers la compulsivité, mais aussi que (dans le modèle de la maladie de Parkinson) la dénervation de la voie nigrostriée et les traitements substitutifs dopaminergiques amplifient l'état impulsif. D'où l'interaction complexe entre le trait impulsif, les traitements et le processus dégénératif. Enfin, nous démontrons le bénéfice thérapeutique de la stimulation de la portion antérieure du pallidum interne dans les formes sévères de tics et suggérons dans un modèle préclinique d'une grande valeur heuristique, que le trait impulsif prédit l'efficacité de la stimulation du core du noyau accumbens. Nos résultats démontrent l'intérêt de mieux caractériser le trait impulsif des patients présentant des désordres compulsifs (syndrome de Gilles de la Tourette, maladie de Parkinson) et ouvrent ainsi de nouvelles perspectives thérapeutiques, tant pour la prévention de la transition de l'impulsivité à la compulsivité, que dans le traitement de ceux-ci. / Impulsivity, a multidimensional trait, determines the severity of compulsive disorders (Tourette's syndrome, Parkinson's disease, obsessive compulsive disorders), but the impulsive / compulsive relation remains unclear. The aim of this work is to identify the neurobiological substrates of impulsive / compulsive balance, using causal manipulations in rats and correlational studies in patients. The results demonstrate - for the first time beside the field of addiction - that, not only high impulsive trait is a transnosological endophenotype of increased vulnerability to develop compulsive disorders, but also that the transition from impulsivity toward compulsivity depends upon the noradrenergic transmission. Furthermore, we also show that, in a Parkinson's disease preclinical model, both the nigrostriatal denervation and dopaminergic treatments increase impulsive state, thereby indicating the contribution of a complex interaction between impulsive trait, medications and neurodegenerative process to the impulsive/compulsive balance. Finally, we show the therapeutic benefit of anterior globus pallidus interna in severe forms of tics and suggest in a preclinical model, with great heuristic value, that impulsive trait predicts the efficacy of nucleus accumbens core stimulation. Together, our results demonstrate the need to address the impulsive/compulsive balance in compulsive disorders and show promise for developing new pathophysiological-based therapeutic strategies that will treat both impulsivity and compulsivity.

In the last decade, (non)prescription opioid abuse, opioid use disorder (OUD) diagnoses, and opioid-related overdoses have risen and represent a significant public health concern. One method of understanding OUD is as a disorder of choice that requires choosing opioid rewards at the expense of other nondrug rewards. The characterization of OUD as a disorder of choice is important as it implicates decision- making processes as therapeutic targets, such as the valuation of opioid rewards. However, reward-value measurement and interpretation are traditionally different in substance abuse research compared to related fields such as economics, animal behavior, and neuroeconomics and may be less effective for understanding how opioid rewards are valued. The present research therefore used choice procedures in line with behavioral/neuroeconomic studies to determine if drug-associated decision making could be predicted from economic choice theories. In Experiment 1, rats completed an isomorphic food-food probabilistic choice task with dynamic, unpredictable changes in reward probability that required constant updating of reward values. After initial training, the reward magnitude of one choice subsequently increased from one to two to three pellets. Additionally, rats were split between the Signaled and Unsignaled groups to understand how cues modulate reward value. After each choice, the Unsignaled group received distinct choice-dependent cues that were uninformative of the choice outcome. The Signaled group also received uninformative cues on one option, but the alternative choice produced reward-predictive cues that informed the trial outcome as a win or loss. Choice data were analyzed at a molar level using matching equations and molecular level using reinforcement learning (RL) models to determine how probability, reward magnitude, and reward-associated cues affected choice. Experiment 2 used an allomorphic drug versus food procedure where the food reward for one option was replaced by a self-administered remifentanil (REMI) infusion at doses of 1, 3 and 10 μg/kg. Finally, Experiment 3 assessed the potential for both REMI and food reward value to be commonly scaled within the brain by examining changes in nucleus accumbens (NAc) Oxygen (O2) dynamics. Results showed that increasing reward probability, magnitude, and the presence of reward-associated cues all independently increased the propensity of choosing the associated choice alternative, including REMI drug choices. Additionally, both molar matching and molecular RL models successfully parameterized rats’ decision dynamics. O2 dynamics were generally commensurate with the idea of a common value signal for REMI and food with changes in O2 signaling scaling with the reward magnitude of REMI rewards. Finally, RL model-derived reward prediction errors significantly correlated with peak O2 activity for reward delivery, suggesting a possible neurological mechanism of value updating. Results are discussed in terms of their implications for current conceptualizations of substance use disorders including a potential need to change the discourse surrounding how substance use disorders are modeled experimentally. Overall, the present research provides evidence that a choice model of substance use disorders may be a viable alternative to the disease model and could facilitate future treatment options centered around economic principles.

Drug-specific reward and associated effects on neural signaling are often studied between subjects, where one group self-administers drug and a separate group self-administers a natural reinforcer. However, exposure to drugs of abuse can cause long-term neural adaptations that can affect how an organism responds to drug reward, natural reward, and their reward-associated stimuli. Thus, to isolate drug-specific effects it is important to use models that expose the same organism to all of the aforementioned. Multiple schedules provide a means of dissociating the rewarding effects of a drug from the rewarding effects of food within a single animal. Further, drug users do not take drugs in isolation; rather, they are often faced with several concurrently available commodities (e.g. monetary goods, social relationships). Thus, using choice measures to assess the relative subjective value of drug reinforcers in both humans and animals promotes a translational understanding of mechanisms that govern drug-associated decision-making. Thus, in order to gain a more translational view of the neurobehavioral mechanisms that underlie drug-associated behavior, in the first study, glutamate was measured in the nucleus accumbens core (NAcC) and prefrontal cortex (PrL) in freely-moving rats as they behaved in a cocaine-food multiple schedule procedure. In the second study, oxygen dynamics were measured in the orbitofrontal cortex (OFC) of freely-moving rats as they behaved in a cocaine/food choice procedure. The results from the first study showed that, in the NAc and PrL, there was an increase in glutamate release when animals earned cocaine. Further, the number of glutamate peaks that occurred per cocaine lever press and per cocaine reinforcer was increased compared to food. In the second study, OFC oxygen dynamics were positively correlated with cocaine/food choice and generally tracked preference. Further, OFC oxygen dynamics were greater to cocaine related events. Taken together, these results showed the feasibility of combining electrochemical measurements with complex drug-related behavioral procedures. These results also highlight the importance of the PrL, NAcC, and OFC in the valuation of drug and non-drug commodities. Overall, these results add to our understanding of the neurobehavioral mechanisms that guide drug-associated behavior and create more precise experimental avenues to research potential treatments.

Le noyau accumbens (NAc) intègre des informations cognitives et affectives. Bien que le rôle du NAc dans les troubles neuropsychiatriques soit bien connu, une compréhension détaillée de ses circuits dans des conditions physiologiques fait défaut. Les neurones moyens épineux (MSNs) du NAc sont des neurones de projection GABAergiques qui expriment des récepteurs D1 ou D2. Ils reçoivent et intègrent des signaux glutamatergiques provenant notamment du cortex préfrontal (PFC), de l'hippocampe ventral (vHipp) et de l'amygdale basolatérale (BLA).Dans cette thèse, nous avons combiné des méthodes optogénétique et électrophysiologique pour dresser un portrait fonctionnel des synapses excitatrices sur les MSNs D1 et D2 dans le NAc de souris adulte. Nous avons observé que les MSNs D1 sont plus excitables que les D2. Ensuite, les propriétés synaptiques de vHipp, de la BLA et du PFC ont révélé une hiérarchie des afférences dépendant de l’identité des MSNs et de l’inhibition «feedforward». Nous avons constaté que la BLA est la voie dominante sur les MSNs D1, tandis que le PFC domine sur les D2. De plus, nous avons testé l’hypothèse que le système endocannabinoïde confère aux circuits excitateurs une plasticité spécifique des voies et des cellules. Ainsi, alors que les récepteurs CB1 dépriment uniformément les voies quelle que soit l’identité des MSNs, les récepteurs TRPV1 contrôlent les afférences de manière bidirectionnelle sur le NAc. Enfin, nous avons clarifié comment l'interaction des récepteurs TRPV1/CB1 façonne la plasticité au niveau des synapses identifiées de BLA-NAc. Ensemble, ces données révèlent un haut degré de spécificité des synapses et du circuit dans le NAc adulte. / The nucleus accumbens (NAc) plays a key role in action selection by integrating cognitive and affective information. The NAc is implicated in numerous neuropsychiatric disorders, however a complete understanding of its circuits and their regulation in physiological conditions is missing. The principal cell type in the NAc, medium-spiny neurons MSNs are GABAergic projection neurons that express either D1 or D2 receptors. They receive and integrate glutamatergic inputs most notably from the prefrontal cortex (PFC), ventral hippocampus (vHipp) and basolateral amygdala (BLA).We combined optogenetic and electrophysiological methods to draw a functional portrait of excitatory disambiguated synapses onto D1 and D2 MSNs in the adult mouse NAc core. We first observed that adult D1- are inherently more excitable than D2-MSNs. Next, the synaptic properties of vHipp, BLA and PFC inputs revealed a hierarchy of synaptic inputs dependent on the identity of the postsynaptic target MSN and on circuit specific feedforward inhibition. We found that the BLA is the dominant excitatory pathway onto D1- while PFC inputs dominate D2-MSNs. Additionally, we tested the hypothesis that the endocannabinoid system endows excitatory circuits with pathway- and cell-specific plasticity. Thus, while CB1 receptors (CB1R) uniformly depress excitatory pathways irrespective of MSNs’ identity, TRPV1 receptors (TRPV1R) bidirectionally control inputs onto the NAc core in a pathway- and cell- specific manner. Finally, we clarified how the interplay of TRPV1R/CB1R shapes plasticity at identified BLA-NAc synapses. Together these data reveal a high degree of synapse and circuit specificity in the adult NAc core.

過去有關壓力的研究指出，當對實驗動物施予單次禁錮、足部或尾部電擊或是實驗者的抓取動作等壓力源時，其大腦中的前額葉皮質、杏仁核、依核或是紋狀體等處會有隨壓力源產生的多巴胺分泌量增加現象。相對於壓力源對腦中神經化學物質的探討，壓力源對與學習制約有關的行為影響的相關研究證據迄今如缺，因此本研究企圖建立單次壓力源操弄對場地制約偏好行為的動物模式。實驗一A對大白鼠施予單次30分鐘的高台壓力源，發現確實可建立場地制約偏好行為。實驗一B操弄單次高台壓力源觀察其對實驗動物自發性活動量的影響，結果發現其對於實驗受試在大動作持續時問上具有抑制效果。實驗一C操弄單次高台壓力源後的0、30、60及120分鐘時採取實驗受試的前額葉皮質、海馬體、杏仁核、依核及紋狀體等五處組織，檢驗其多巴胺、血清張力素及代謝物的含量。結果發現除海馬體外的四個部位的多巴胺量及其代謝物分別在不同採集時間點有不等的顯著增加現象。血清張力素的變化量在各個部位不及多巴胺。實驗二及實驗三分別經由周邊或中樞前額葉皮質微量注射多巴胺D₁與D₂專屬受體拮抗劑，結果發現其可抑制曲單次高台壓力源操弄所建立的場地制約偏好行為。綜合上述結果，單次高台壓力源的操弄確實可引發大白鼠大腦中的多巴胺量增加藉以形成場地制約偏好行為，而此場地制約偏好行為所依賴的多巴腰量增加位置推論其是依核而非前額葉皮質。另外，多巴胺D1與D2受體對此高台壓力源引發的場地制約偏好行為所扮演的角色相當。 / When experimental animals under single stressor, such as restraint, foot, or tail-shock, or handing, an immediate and robust releasing of dopamine appears in the prefrontal cortex, amygdala, nucleus accumbens, or striatum. In contrast to these neurochemical findings, the behavioral effects under stress are rarely studied and remained uncertain. The purpose of this study was to establish an animal model of single stress-induced conditioned place preference (CPP). Experiment 1A found that the CPP can be induced by a single high-plate stressor. Experiment 1B investigated the effects of this single high plate stressor on rats' locomotion, this stressor was found to inhibit the large movement as measured by duration. Experiment 1C investigated the timing course of this stressor on dopamine, serotonin, and their metabolities in the prefrontal cortex, hippocampus, amygdala, nucleus accumbens, and striatum. The results showed that all the areas, except hippocampus, had distinct patterns of changes on dopamine, serotonin and their metabolities at different times' after stress. Experiment 2 and 3, examined the effects ofdopamine D1 or D2 receptor antagonists, administered respectively via intraperitoneal or local infusion into the prefrontal cortex, on the CPP formed after high-plate stress. The results showed that these drug manipulations can inhibit stress-induced CPP. Taken together, these results indicated the CPP formed after high-plate stressor is developed on the immediate increase ofdopamine releases in the nucleus accumbens and prefrontal cortex. These neurochemical alterations are more profound in the nucleus accumbens than the prefrontal cortex. However, the dopamine D₁ and D₂ receptor in the prefrontal cortex are also important for the formation of CPP after high-plate stressor.