Stress promotes the use of methamphetamine and other recreational substances and is often implicated in relapse to stimulant use. Thus, it is of critical importance to examine the consequences of the co-occurance of stress and methamphetamine use. Activity of the glutamatergic N-methyl D-aspartate (NMDA) receptor system appears to be involved in the neurotoxic effects of both chronic stress and methamphetamine exposure. The current studies investigated the hypothesis that chronic pre-exposure to the stress hormone corticosterone (CORT) results in an increase of NMDA receptor activity and that this will potentiate the neurotoxic effects of methamphetamine (METH). Co-cultures of the ventral tegmental area, nucleus accumbens, and medial prefrontal cortex were pre-exposed to CORT (1 μM) for 5 days prior to co-exposure to METH (100 μM) for 24 hours to investigate the combined effects on neurotoxicity and protein density of NMDA receptor subunits. The combination of CORT and METH resulted in significant neurotoxicity within the medial prefrontal cortex compared to either CORT or METH alone. The CORT+METH-induced toxicity was attenuated by co-exposure to the NMDA receptor antagonist (2R)-amino-5-phosphonovaleric acid (APV; 50 μM) during the 24 hour CORT and METH co-exposure. Although CORT alone did not significantly alter the density of the NR1 and NR2B subunits of the NMDA receptor, METH exposure for 24 hours resulted in a significant loss of the polyamine sensitive NR2B subunit. Co-exposure to CORT and METH also resulted in decreased extracellular glutamate while not significantly altering extracellular dopamine. These results suggest an enhancement of NMDA receptor systems or downstream effectors in areas of the mesolimbic reward pathway following chronic pre-exposure to CORT, which leads to enhanced neuronal vulnerability to future excitotoxic insults. This may be of critical importance as use of psychostimulants such as METH and other drugs of abuse may produce excitotoxic events in these areas, thus further compromising neuronal viability.

Projections from the Nucleus Accumbens (NAc) to the Ventral Pallidum (VP) play a critical role in motivation and reward. Rewards and reward-associated cues are thought to alter this pathway by suppressing GABA release to the VP, however, the role of the NAc to VP pathway has never been investigated with regard to nicotine self-administration. We hypothesized that increasing GABAergic signaling from the NAc to the VP would decrease the reinforcing effects of nicotine. To increase GABA release, CRE dependent DREADD was expressed in the NAc of male rats. Administration of low dose clozapine activated the DREADD receptor and showed a reduction in responding for nicotine suggesting that activation of the NAc to VP pathway reduced reinforcement. However, a nonspecific effect was observed leading to future investigation of locomotor activity. Immunohistochemistry and microdialysis were used to confirm DREADD expression in the NAc and increased extracellular GABA in the VP.

The aim of the two studies presented here was to evaluate the effects of cocaine and mefloquine (MFQ) on γ-aminobutyric acid (GABA) and dopamine (DA) neurons in the ventral tegmental area (VTA). Cocaine: In vivo, lower doses of intravenous cocaine (0.25-0.5 mg/kg), or methamphetamine (METH), enhanced VTA GABA neuron firing rate via D2/D5 receptor activation. Higher cocaine doses (1.0-2.0 mg/kg) inhibited their firing rate. Cocaine and lidocaine inhibited the firing rate and spike discharges induced by stimulation of the internal capsule (ICPSDs) at dose levels 0.25-2 mg/kg (IC50 1.2 mg/kg), but neither DA nor METH reduced ICPSDs. In VTA GABA neurons in vitro, cocaine reduced (IC50 13 µM) current-evoked spikes and sodium currents in a use-dependent manner. In VTA DA neurons, cocaine reduced IPSCs (IC50 13 µM), increased IPSC paired-pulse facilitation, and decreased sIPSC frequency, without affecting mIPSC frequency or amplitude. These findings suggest cocaine reduces activity-dependent GABA release on DA neurons in the VTA, and that cocaine's use-dependent blockade of VTA GABA neuron voltage-sensitive sodium channels (VSSCs) may synergize with its DAT inhibiting properties to enhance mesolimbic DA transmission implicated in cocaine reinforcement. Mefloquine: Mefloquine (MFQ) is an anti-malarial agent, Connexin-36 (Cx36) gap junction blocker, 5-HT3 antagonist, and calcium ionophore. Mounting evidence of a Cx36-mediated VTA GABA neuron syncytium suggests MFQ-related dysphoria may attribute to its gap junction blocking effects on VTA synaptic homeostasis. We observed that MFQ (25 µM) increased DA neuron spontaneous IPSC frequency 6 fold, and mIPSC 3 fold. Carbenoxolone (CBX, 100 µM) only increased sIPSC frequency 2 fold, and did not affect DA mIPSC frequency. Ondansetron did not mimic MFQ. Additionally, MFQ did not affect VTA DA evoked IPSC paired pulse ratio (PPR). However, Mefloquine did induce a 3.5 fold increase in bath-applied GABA current. Remarkably, MFQ did not affect VTA GABA neuron inhibition. At VTA DA neuron excitatory synapses MFQ increased sEPSC frequency in-part due to an increase in the AMPA/NMDA ratio. These finding suggest MFQ alters VTA synapses differentially depending on neuron and synapse type, and that these alterations appear to involve MFQ's gap junction blocking and calcium ionophore actions.

Cholinergic inputs from mesopontine tegmentum activate midbrain dopamine (DA) neurons via M5 muscarinic receptors. The M5 receptor is important for mesopontine stimulation-induced accumbal or striatal DA efflux, brain stimulation reward or morphine-induced conditioned place preference (CPP). M5 receptor knockout (KO) mice show 40-50% less morphine-induced locomotion. Pedunculopontine tegmental nucleus (PPT) lesions in rodents block morphine CPP, but are ineffective after 18 hours food deprivation, opiate dependence, or intra-VTA BDNF. Based on these findings, we investigated whether acute food deprivation or intra-VTA BDNF alters morphine-induced locomotion (3 and 10 mg/kg, i.p.) in C57BL/6 M5 KO mice. Non-deprived M5 KOs showed reduced morphine-induced locomotion, suggesting M5 receptors partly mediate morphine-induced locomotion. Morphine-induced locomotion was reversed in food-deprived mice, suggesting the stimulant effects of morphine were altered to bypass the PPT. Unexpectedly, intra-VTA BDNF infusions were ineffective in altering morphine-induced locomotion. Additionally, M5 KOs receiving intra-VTA saline showed no deficits in morphine-induced locomotion.

Cholinergic inputs from mesopontine tegmentum activate midbrain dopamine (DA) neurons via M5 muscarinic receptors. The M5 receptor is important for mesopontine stimulation-induced accumbal or striatal DA efflux, brain stimulation reward or morphine-induced conditioned place preference (CPP). M5 receptor knockout (KO) mice show 40-50% less morphine-induced locomotion. Pedunculopontine tegmental nucleus (PPT) lesions in rodents block morphine CPP, but are ineffective after 18 hours food deprivation, opiate dependence, or intra-VTA BDNF. Based on these findings, we investigated whether acute food deprivation or intra-VTA BDNF alters morphine-induced locomotion (3 and 10 mg/kg, i.p.) in C57BL/6 M5 KO mice. Non-deprived M5 KOs showed reduced morphine-induced locomotion, suggesting M5 receptors partly mediate morphine-induced locomotion. Morphine-induced locomotion was reversed in food-deprived mice, suggesting the stimulant effects of morphine were altered to bypass the PPT. Unexpectedly, intra-VTA BDNF infusions were ineffective in altering morphine-induced locomotion. Additionally, M5 KOs receiving intra-VTA saline showed no deficits in morphine-induced locomotion.

Made available in DSpace on 2016-06-02T19:22:56Z (GMT). No. of bitstreams: 1 4388.pdf: 1226815 bytes, checksum: 90cf9ba0ac00628538f6b744e2c5bac1 (MD5) Previous issue date: 2011-02-25 / Financiadora de Estudos e Projetos / Estrogen is a steroid hormone known to play a role in cellular events important for development, maintenance of body physiology and modulatory actions on central nervous system during life. The aim of this study was to investigate the effect of ovariectomy (OVX) and the intervention of strength training on the tissue concentrations of dopamine (DA) and serotonin (5-HT) in the nigrostriatal and mesolimbic pathways in female rats. Also, check behavioral parameters of exploratory activity in novel environment, in testing of the plus maze (EPM) and open field (CA). Female rats were divided into four groups: Sedentary (Sed- Intact), ovariectomized Sedentary (Sed-OVX) Trained intact (Intact-ExCrônico) Trained ovariectomized (OVX-ExCrônico) (n = 10 per group). We conducted a period of 12 weeks of strength training which consisted of increases in a vertical ladder of 1.1 meters, weight tied to its tail. The sessions were held once every three days with 4-9 and 8-12 uphill climb for motion. The OVX caused changes in tissue concentrations of DA and 5-HT in the mesolimbic and nigrostriatal pathways. However strength training has not been able to revet these changes. In behavioral tests of anxiety were observed behavior and decrease the exploratory activity of rats in the independent training (OVX). The results of this study showed that OVX alters the state of the tissue concentrations of DA and 5-HT but these changes seem to depend on the type of receptor and its topographic distribution. Strength training has not been able to reverse these changes. / O estrogênio é um hormônio esteróide conhecido por representar um papel relevante nos eventos celulares do desenvolvimento, manutenção da fisiologia do corpo e ações moduladoras no sistema nervoso central (SNC) durante a vida. O objetivo do presente estudo foi investigar o efeito da ovariectomia (OVX) e da intervenção do treinamento de força sobre as concentrações teciduais de dopamina (DA) e serotonina (5- HT) nas Vias Nigroestriatal e Mesolímbicas em ratas. Além disso, verificar parâmetros comportamentais de atividade exploratória em ambiente novo, nos testes do labirinto em cruz elevado (LCE) e campo aberto (CA). Ratas fêmeas foram divididas em quarto grupos: Sedentário (Sed-Intacto); Sedentário ovariectomizado (Sed-OVX); Treinado intacto (ExCrônico-Intacto); Treinado ovariectomizado (ExCrônico-OVX) (n = 10 por grupo). Foi realizado um período de 12 semanas de treinamento de força que consistia em subidas em uma escada vertical de 1,1 metros, com peso atado a cauda. As sessões foram realizadas uma vez a cada três dias com 4-9 subidas e 8-12 movimentos por escalada. A OVX causou alterações na concentração tecidual de DA e 5-HT nas Vias Mesolímbica e Nigroestriatal . No entanto o treinamento de força não foi capaz de reverter essas alterações. Nos testes comportamentais foi observado comportamento de ansiedade e decréscimo da atividade exploratória dos animais submetidos ao treinamento, independente da OVX. Os resultados deste estudo mostram que o estado de OVX altera as concentrações teciduais de DA e 5- HT, no entanto essas alterações parecem depender do tipo de receptor e da sua distribuição topográfica. O treinamento de força não foi capaz de reverter essas alterações.

No description available.

「風險決策」行為非常普遍的存在於吾人之日常生活中，而選項所帶來的風險和獎勵是吾人進行決策時的重要考量因素。風險選擇的適當與否，對於個體的生存扮演著相當重要的角色。在以往的文獻中，對於決策的行為歷程已有所關注及探討，但對於風險選擇行為的神經生理機制迄今未明。本研究藉由大白鼠於T字迷津中，選擇確定之低酬賞或高不確定性之高酬賞的行為表現，進行風險選擇行為的探討。本研究中以兩項主要實驗，探討風險選擇行為之神經行為機制。實驗1a中，確定之低酬賞端固定呈現1顆食物粒，而高不確定性之高酬賞端則同時操弄酬賞物機率(50%、25%及12.5%)以及酬賞物的量(2、4及8顆)，以系統性地檢驗期望值(0.5、1和2)於此風險選擇行為中扮演的角色。行為結果顯示當風險較低時，大白鼠會選擇高不確定性之高酬賞端；而風險較高時，則轉為選擇確定之低酬賞端。實驗1b中，系統性地施打不同劑量之安非他命，探討多巴胺系統在此風險選擇行為中之機制。實驗結果顯示施打安非他命後，大白鼠表現出相對地追求風險之行為，亦即選擇高不確定之高酬賞端之比例顯著高於控制組。實驗2中，藉由毀除大腦特定部位(依核、背外側之紋狀體、眶前額皮質、內側之前額皮質)，檢驗風險選擇行為之神經基礎。毀除後之結果顯示，僅有依核受到毀除之大白鼠表現出相對地趨避風險之選擇行為。綜合以上結果，本研究建立之風險選擇行為與多巴胺有關，而依核在此行為歷程中扮演重要的調節角色。 / Many decisions people make every day involve uncertainty where both risks and rewards associated with each option need to be considered. Behavioral performance associated to risk-based choice appears wildly over the lifespan, and the fitness of risky choice behavior plays an important role in individual survival. Despite a growing body of research has focused to investigate the neurobiology of decision making, little is known about the neurobehavioral mechanisms of risky choice behavior. Based on a pilot work, this study used a T-maze to study decision under a probability-based risk in the rat. The subject was assessed on making choice to obtain either a large reward associated with risk of non-reward “empty” or a small reward ensured for every entry. Two experiments were conducted in this project to investigate neurobehavioral mechanisms of probabilistic risky choice behavior. In Experiment 1a, probabilistic risky choice behavior was systemically assessed under three expected values (0.5, 1.0, and 2.0) by manipulating the probabilities of reward presence (50%, 25%, and 12.5%) and the reward magnitude (2, 4, or 8 pellets) in the probabilistic high reward (PHR) arm. Behavioral data showed that the subject chose the probabilistic high reward in a lower risk condition but would shift to the choice of certain low reward (CLR) as the risk is increased. In Experiment 1b, the dose effects of amphetamine on this probabilistic risky choice task was tested to verify whether the dopaminergic mechanism was involved. Amphetamine, presumably activating brain dopamine systems, produced a relatively risk-seeking effect on the present behavioral task. In Experiment 2, the excitoneurotoxic lesion was conducted in the nucleus accumbens, the dorsolateral striatum, the orbitofrontal cortex, and the medial prefrontal cortex to examine the neural substrates for this probabilistic risky choice behavior. The results showed that the lesion of the nucleus accumbens significantly produced a relatively risk-averse effect on the present behavioral task, as compared to the lesions made on the other three brain areas. In conclusion, the probabilistic risky choice behavior established in the present study is dopamine dependent. And, the nucleus accumbens plays a major role of mediating this behavioral processing.

L'obésité, caractérisée par une prise de poids excessive et un état inflammatoire, est une maladie métabolique qui devrait être prévenue car elle constitue un facteur de risque pour les maladies cardio-métaboliques. Les régimes riches en énergie et en graisses (high fat diet - HFD) sont une des causes de l'obésité. Plusieurs études suggèrent que les lipides alimentaires peuvent modifier la signalisation neuronale, l’excitabilité et la connectivité dans les aires cérébrales impliquées dans l’homéostasie énergétique. Dans le cerveau, les acides gras (AG) modulent la prise alimentaire, la prise de poids, et, plus récemment décrit, la motivation à obtenir de la nourriture. Ces effets semblent être médiés par l'incorporation des AG et/ou par leur métabolisme intra-neuronal, des mécanismes qui sont facilités par les protéines de transport, en particulier FATP1 (fatty acid transport protein-1). Il a aussi été montré que l’obésité altère l’intensité de l’effet de la dopamine (DA) et la neurotransmission dopaminergique dans le système mésolimbique, bien reconnu pour son implication dans les systèmes de récompense. Certaines études suggèrent que les neurones DA sont capables d’intégrer les AG, et que l'oléate, un acide gras à longue chaîne (AGLC), agit sur les neurones dans l’aire tegmentale ventrale (ventral tegmental area - VTA) d'où sont issus les neurones DA. L’oléate inhiberait l’activité neuronale dopaminergique, et donc les comportements de récompense. Cependant, notre compréhension du métabolisme des AG et de leur incorporation dans le VTA est encore trop partielle. Nous avons voulu : 1) mesurer la captation d’un analogue radiomarqué d’AGLC, le *FTHA, dans diverses régions du cerveau impliquées dans la régulation de la prise alimentaire; 2) vérifier si le blocage pharmacologique de l’entrée des AG dans les cellules, via un inhibiteur de FATP1, module les effets suppresseurs de l'oléate sur la récompense alimentaire lorsqu’injecté dans le VTA; et 3) évaluer les effets d’une longue HFD sur l’accumulation de graisse dans le cerveau, la neuroinflammation, et sur la barrière hémato- encéphalique (brain blood barrier - BBB) dans les régions impliquées dans la récompense. Pour l’objectif 1, nous avons élaboré un protocole permettant de quantifier l’incorporation et l’accumulation d’AG dans le cerveau. Après une injection de *FTHA dans la veine de la queue des souris, leurs cerveaux ont été disséqués, et la radioactivité était mesurée avec un compteur gamma. Nous avons montré que le cortex préfrontal et certaines zones associées au système de récompense (striatum dorsal-DS, VTA et noyau accumbens-NAC), mais pas l'hypothalamus médiobasal (mediobasal hypothalamus – MBH), incorporent le *FTHA. De plus, le VTA et le DS affichaient des taux de radioactivité plus importants et, plus rapidement, que les autres zones d’intérêt. Nous avons aussi déterminé que 15 minutes est le temps d'incubation optimal pour mesurer le *FTHA. Pour l’objectif 2, nous avons confirmé in vitro l’action de l’inhibiteur de la FATP1. Cependant, contrairement à des travaux antérieurs de notre équipe, nous n'avons pas trouvé de différence dans les comportements de récompense suite à des injections intra-VTA d'oléate et/ou de l’inhibiteur de la FATP1. Pour l’objectif 3, des souris ont été nourries soit avec une HFD riche en AG saturées, soit avec une diète contrôle durant 20 semaines. Elles sont devenues obèses et, via des techniques immunohistochimiques, nous avons montré que la HFD avait induit une plus grande activation microgliale dans le VTA et le NAC, ainsi qu’une plus grande perméabilité de la BBB au niveau du VTA. En revanche, nous n’avons pas trouvé de différences pour la teneur en lipides, le nombre de microglies, ou les protéines de jonction de la BBB. L'interprétation de nos résultats tient compte de certaines limites dues à nos approches méthodologiques et à la petite taille de nos échantillons. Néanmoins, s’ils sont confirmés, nos travaux pourraient contribuer à mieux comprendre comment les AG circulants sont incorporés dans le cerveau. Nous avons démontré que les AGLC traversent la BBB et s’accumulent dans plusieurs zones de récompense (DS, VTA) de façon plus importante que dans le MBH, une région réputée pour être associée à l’homéostasie énergétique et à la détection des nutriments. Nous avons aussi montré que l’obésité induite par l’HFD est associée à une augmentation de la perméabilité de la BBB dans le VTA, et que l’on peut étendre au VTA la relation entre l’obésité et la neuroinflammation. Notre travail apporte de nouvelles données dans le domaine du métabolisme et de l’incorporation des AG circulants dans le cerveau ainsi que sur les conséquences potentielles d’une exposition prolongée à une HFD. Comme les AG semblent s’accumuler dans le système de récompense et qu’ils pourraient modifier le comportement alimentaire des humains, nos résultats pourraient avoir des implications en obésité. / Obesity is a preventable metabolic disorder characterized by excessive weight gain and inflammation, which predisposes to numerous cardiometabolic diseases. One of the causes of obesity is the continued consumption of an energy dense, high-fat diet (HFD). Increasing evidence suggests that lipid nutrients can modify neural signaling, excitability and connectivity in brain areas involved in energy homeostasis. Moreover, fatty acids (FA) in the brain have been shown to modulate food intake, weight gain, and, more recently, food-motivated behavior. These effects seem to be mediated by FA uptake and intra-cellular metabolism, which is facilitated by FA transport proteins such as FATP1. Obesity has been shown to induce alterations in dopamine (DA) tone and signaling in the mesolimbic system, well known for its implication in reward. Evidence suggests that DA neurons detect FAs and that oleate, a long chain fatty acid (LCFA), acts on neurons in the ventral tegmental area (VTA), where DA neurons originate, to suppress DA neural activity and food-seeking. However, our understanding of FA metabolism and its uptake into VTA is still to be refined. We sought to evaluate whether: 1) the incorporation of a radiolabeled LCFA analog, *FTHA, in brain regions implicated in the regulation of food intake; 2) blocking FA entry into cells of the VTA, using a pharmacological inhibitor of FATP1, modulates the suppressive effects of oleate on food-motivated behavior; and 3) prolonged HFD has effects on fat accumulation, neuroinflammation, and blood brain barrier (BBB) integrity and leakage in reward-related areas. Under objective 1, we developed a protocol to allow the quantification of FA uptake in the brain using tail-vein injections of *FTHA, brain dissections, and gamma counter. We found that the prefrontal cortex and reward-related areas (dorsal striatum [DS], VTA and nucleus accumbens [NAC]), but not the mediobasal hypothalamus (MBH), incorporate *FTHA, that the VTA and DS emitted proportionally more radioactivity, and may do so more rapidly, than the other brain regions assessed. We also determined that a 15-minute incubation was optimal for *FTHA detection. Under objective 2, we showed in vitro a reduction in lipid accumulation in neurons after FATP1 inhibition. However, contrary to previous experiments conducted in our lab, we found no significant difference in food-motivated behavior following an intra-VTA oleate and/or FATP1 inhibitor injection. Under objective 3, mice were fed either a HFD (high saturated FAs) or a control diet for 20 weeks. They became obese, and via immunohistochemical techniques, we found that HFD induced greater microglial activation in the VTA and NAC, and greater BBB permeability in the VTA. However, we did not find differences in cerebral lipid content, number of microglial cells, or changes in BBB tight junction proteins. Interpretation of these experiments are discussed within certain methodological limitations and the small size of our samples. Nonetheless, if confirmed, our data may provide additional insight in the transport of peripheral FAs into the brain. We showed that LCFA pass through BBB and accumulate in reward-related areas. The VTA, and DS had significantly greater accumulation of *FTHA compared to the MBH, a region traditionally associated with energy homeostasis and nutrient sensing. We also showed that diet-induced obesity is associated with increased BBB permeability in the VTA, and we extended the established relationship between obesity and neuroinflammation to the VTA. This work brings forth new insights in the realm of FA uptake and metabolism in the brain, as well as their potential impacts after prolonged exposure. Our data may have potential implications for obesity, as this facilitates this macronutrient uptake in the reward system, and may alter postprandial food-seeking behaviors in humans.

Indiana University-Purdue University Indianapolis (IUPUI) / Alcohol and cocaine are commonly co-abused drugs, and those meeting criteria for both cocaine and alcohol use disorders experience more severe behavioral and health consequences than those with a single disorder. Chronic alcohol (ethanol) drinking increased the reinforcing and dopamine (DA) neuronal stimulating effects of ethanol within mesolimbic regions of the central nervous system (CNS) of alcohol-preferring (P) rats. The objectives of the current study were to determine if chronic continuous ethanol drinking produced: (1) alterations in the sensitivity of the nucleus accumbens shell (AcbSh) to the reinforcing effects of cocaine, (2) changes in the magnitude and time course of the local stimulating effects of cocaine on posterior ventral tegmental area (pVTA) DA neurons, and (3) a persistence of alterations in the stimulating effects of cocaine after a period of protracted abstinence. Female P rats received continuous, free-choice access to water and 15% v/v ethanol for at least 10 wk (continuous ethanol-drinking; CE) or access to water alone (ethanol-naïve; N). A third group of rats received the same period of ethanol access followed by 30 d of protracted abstinence from ethanol (ethanol-abstinent; Ab). CE and Ab rats consumed, on average, 6-7 g/kg/d of ethanol. Animals with a single cannula aimed at the AcbSh responded for injections of cocaine into the AcbSh during four initial operant sessions. Cocaine was not present in the self-infused solution for the subsequent three sessions, and cocaine access was restored during one final session. Animals with dual ipsilateral cannulae aimed at the AcbSh and the pVTA were injected with pulsed microinfusions of cocaine into the pVTA while DA content was collected for analysis through a microdialysis probe inserted into the AcbSh. During the initial four sessions, neither CE nor N rats self-infused artificial cerebrospinal fluid (aCSF) or 0.1 mM cocaine into the AcbSh. CE, but not N, rats self-administered 0.5 mM cocaine into the AcbSh, whereas both groups self-infused concentrations of 1.0, 2.0, 4.0, or 8.0 mM cocaine. When cocaine access was restored in Session 8, CE rats responded more on the active lever and obtained more infusions of 0.5, 1.0, 2.0, or 4.0 mM cocaine compared to N rats. Microinjection of aCSF into the pVTA did not alter AcbSh DA levels in N, CE, or Ab rats. Microinjections of 0.25 mM cocaine into the pVTA did not significantly alter AcbSh DA levels in N animals, moderately increased DA levels in CE rats, and greatly increased DA levels in Ab rats. Microinjections of 0.5 mM cocaine into the pVTA modestly increased AcbSh DA levels in N animals, robustly increased DA levels in CE rats, and did not significantly alter DA levels in Ab rats. Microinjections of 1.0 or 2.0 mM cocaine into the pVTA modestly increased AcbSh DA levels in N animals but decreased DA levels in CE and Ab rats. Overall, long-term continuous ethanol drinking by P rats enhanced both the reinforcing effects of cocaine within the AcbSh and the stimulatory and inhibitory effects of cocaine on pVTA DA neurons. Alterations in the stimulatory and inhibitory effects of cocaine on pVTA DA neurons were not only enduring, but also enhanced, following a period of protracted abstinence from ethanol exposure. Translationally, prevention of chronic and excessive alcohol intake in populations with a genetic risk for substance abuse may reduce the likelihood of subsequent cocaine use.